Ultimate Calibration
2nd Edition
Beamex is a technology and service company that develops, manufactures and
markets high-quality calibration equipment, software, systems and services for the
calibration and maintenance of process instruments. The company is a leading
worldwide provider of integrated calibration solutions that meet even the most demanding
requirements. Beamex offers a comprehensive range of products and services-from portable
calibrators to workstations, calibration accessories, calibration software, industry-specific
solutions and professional services. Through Beamex’s global and competent partner network,
their products and services are available in more than 60 countries. As a proof of Beamex’s
success, there are more than 10,000 companies worldwide utilizing their calibration solutions.
Several companies have been Beamex’s customer since the establishment of the company
over 30 years ago. For more information about Beamex and its products and services,
visit www.beamex.com
Beamex has used reasonable efforts to ensure that this book contains both accurate
and comprehensive information. Notwithstanding the foregoing, the content of this book is
provided “as is” without any representations, warranties or guarantees of any kind, whether
express or implied, in relation to the accuracy, completeness, adequacy, currency, quality,
timeliness or fitness for a particular purpose of the content and information provided on this
book. The contents of this book are for general informational purposes only. Furthermore, this
book provides examples of some of the laws, regulations and standards related to calibration and
is not intended to be definitive. It is the responsibility of a company to determine which laws,
regulations and standards apply in specific circumstances.
Ultimate Calibration 2nd Edition
Copyright © 2009–2012 by Beamex Oy Ab. All rights reserved.
No part of this publication may be reproduced or distributed in
any form or by any means, or stored in a database or retrieval
system, without the prior written permission of Beamex Oy Ab.
Requests should be directed to info@beamex.com.
Beamex is a trademark of Beamex Oy Ab.
All other trademarks or trade names mentioned in this book
are the property of their respective holders.
Graphic design: Studio PAP
Photos: Mats Sandström and image bank
Printed by: Fram in Vaasa 2012, Finland
Contents
Preface by the CEO of Beamex Group 7
QUALITY, REGULATIONS AND TRACEABILITY
Quality standards and industry regulations
11
A basic quality calibration program 35
Traceable and efficient calibrations in the process industry
57
CALIBRATION MANAGEMENT AND MAINTENANCE
Why Calibrate? What is the risk of not calibrating?
73
Why use software for calibration management? 79
How often should instruments be calibrated?
89
How often should calibrators be calibrated?
97
Paperless calibration improves quality and cuts costs
101
Intelligent commissioning 107
Successfully executing a system integration project
115
CALIBRATION IN INDUSTRIAL APPLICATIONS
The benefits of using a documenting calibrator 125
Calibration of weighing instruments Part 1
131
Calibration of weighing instruments Part 2
137
Calibrating temperature instruments 143
Calculating total uncertainty of temperature calibration with a dry block
Fieldbus transmitters must also be calibrated 157
Configuring and calibrating smart instruments
163
Calibration in hazardous environments 169
The safest way to calibrate to calibrate Fieldbus instruments
APPENDIX: Calibration terminology A to Z 181
175
149
foreword
6
preface by the ceo of beamex group
Preface
C
alibrators, calibration software and other related equipment
have developed significantly during the past few decades in
spite of the fact that calibration of measurement devices as
such has existed for several thousands of years.
Presently, the primary challenges of industrial metrology and
calibration include how to simplify and streamline the entire
calibration process, how to eliminate double work, how to reduce
production down-time, and how to lower the risk of human errors. All
of these challenges can be tackled by improving the level of system
integration and automation.
Calibration and calibrators can no longer be considered as isolated,
stand-alone devices, systems or work processes within a company or
production plant. Just like any other business function, calibration
procedures need to be automated to a higher degree and integrated to
achieve improvements in quality and efficiency. In this area, Beamex
aims to be the benchmark in the industry.
This book is the 2nd edition of Ultimate Calibration. The main
changes to this edition include numerous new articles and a new
grouping of the articles to make it easier to find related topics. The
new topics covered in the edition mainly discuss paperless calibration,
intelligent commissioning, temperature calibration and configuring,
and calibration of smart instruments.
This book is the result of work that has taken place between 2006
and 2012. A team of experts in industry and calibration worldwide has
put forth effort to its creation.
On behalf of Beamex, I would like to thank all of the people who
have contributed to this book. I want to express my special thanks to
Pamela at Beamex Marketing, who was the key person in organizing
and leading the project for the 2nd edition. I hope this book will assist
you in learning new things and in providing fresh, new ideas. Enjoy
your reading!
raimo ahola, ceo, beamex group
7
Quality,
Regulations and
Traceability
quality standards and industry regulations
Calibration requirements
according to quality standards
and industry regulations
B
efore going into what the current standards and regulations
actually state, here is a reminder from times past about
measurement practices and how important they really are.
Immersion in water makes the straight seem bent; but reason, thus
confused by false appearance, is beautifully restored by measuring,
numbering and weighing; these drive vague notions of greater or less
or more or heavier right out of the minds of the surveyor, the computer,
and the clerk of the scales. Surely it is the better part of thought that
relies on measurement and calculation. (Plato, The Republic, 360 B.C.)
There shall be standard measures of wine, beer, and corn…
throughout the whole of our kingdom, and a standard width of dyed
russet and cloth; and there shall be standard weights also. (Clause 35,
Magna Carta, 1215)
When you can measure what you are speaking about and express
it in numbers, you know something about it; but when you cannot
express it in numbers, your knowledge is of a meager and unsatisfactory
kind. It may be the beginning of knowledge, but you have scarcely, in
your thoughts, advanced to the stage of science. (William Thomson,
1st Baron Kelvin, GCVO, OM, PC, PRS, 26 June 1824–17 December
1907; A.K.A. Lord Kelvin).1
One of the earliest records of precise measurement is from Egypt.
The Egyptians studied the science of geometry to assist them in the
construction of the Pyramids. It is believed that about 3000 years B.C.,
the Egyptian unit of length came into being.
The “Royal Egyptian Cubit” was decreed to be equal to the length
of the forearm from the bent elbow to the tip of the extended middle
11
quality standards and industry regulations
finger plus the width of the palm of the hand of the Pharaoh or King
ruling at that time.2
The “Royal Cubit Master” was carved out of a block of granite to
endure for all times. Workers engaged in building tombs, temples,
pyramids, etc. were supplied with cubits made of wood or granite. The
Royal Architect or Foreman of the construction site was responsible for
maintaining & transferring the unit of length to workers instruments.
They were required to bring back their cubit sticks at each full moon
to be compared to the Royal Cubit Master.
Failure to do so was punishable by death. Though the punishment
prescribed was severe, the Egyptians had anticipated the spirit of the
present day system of legal metrology, standards, traceability and
calibration recall.
With this standardization and uniformity of length, the Egyptians
achieved surprising accuracy. Thousands of workers were engaged in
building the Great Pyramid of Giza. Through the use of cubit sticks,
they achieved an accuracy of 0.05%. In roughly 756 feet or 230.36276
meters, they were within 4.5 inches or 11.43 centimeters.
The need for calibration has been around for at least 5000 years.
In today’s calibration environment, there are basically two types of
requirements: ISO standards and regulatory requirements. The biggest
difference between the two is simple – ISO standards are voluntary, and
regulatory requirements are mandatory. If an organization volunteers
to meet ISO 9000 standards, they pay a company to audit them to that
standard to ensure they are following their quality manual and are
within compliance. On the other hand, if a company is manufacturing
a drug that must meet regulatory requirements, they are inspected
by government inspectors for compliance to federal regulations. In
the case of ISO standards, a set of guidelines are used to write their
quality manual and other standard operating procedures (SOPs) and
they show how they comply with the standard. However, the federal
regulations specify in greater detail what a company must do to meet
the requirements set forth in the Code of Federal Regulations (CFRs).
In Europe, detailed information for achieving regulatory compliance
is provided in Eudralex - Volume 4 of “The rules governing medicinal
products in the European Union”.
The Pharmaceutical Inspection Convention and Pharmaceutical
Inspection Co-operation Scheme (PIC/S) aims to improve
harmonisation of Good Manufacturing Practice (GMP) standards
and guidance documents.
12
quality standards and industry regulations
Calibration requirements according to the U. S. Food and Drug
Administration (FDA)
Following are examples of some of the regulations required by
the FDA, and what they say about calibration and what must be
accomplished to meet the CFRs. Please note that European standards
are similar to FDA requirements. Listed below are several different
parts of 21CFR, that relate to the calibration of test equipment in
different situations and environments.
TITLE 21 – FOOD AND DRUGS
CHAPTER I – FOOD AND DRUG ADMINISTRATION
DEPARTMENT OF HEALTH AND HUMAN SERVICES
SUBCHAPTER H – MEDICAL DEVICES
PART 820 QUALITY SYSTEM REGULATION 22
Subpart A – General Provisions
§ 820.1 – Scope.
§ 820.3 – Definitions.
§ 820.5 – Quality system.
Subpart B – Quality System Requirements
§ 820.20 – Management responsibility.
§ 820.22 – Quality audit.
§ 820.25 – Personnel.
Subpart C – Design Controls
§ 820.30 – Design controls.
Subpart D – Document Controls
§ 820.40 – Document controls.
Subpart E – Purchasing Controls
§ 820.50 – Purchasing controls.
Subpart F – Identification and Traceability
§ 820.60 – Identification.
§ 820.65 – Traceability.
Subpart G – Production and Process Controls
§ 820.70 – Production and process controls.
§ 820.72 – Inspection, measuring, and test equipment.
§ 820.75 – Process validation.
13
quality standards and industry regulations
Subpart H – Acceptance Activities
§ 820.80 – Receiving, in-process, and finished device acceptance.
§ 820.86 – Acceptance status.
Subpart I – Nonconforming Product
§ 820.90 – Nonconforming product.
Subpart J – Corrective and Preventive Action
§ 820.100 – Corrective and preventive action.
Subpart K – Labeling and Packaging Control
§ 820.120 – Device labeling.
§ 820.130 – Device packaging.
Subpart L – Handling, Storage, Distribution, and Installation
§ 820.140 – Handling.
§ 820.150 – Storage.
§ 820.160 – Distribution.
§ 820.170 – Installation.
Subpart M – Records
§ 820.180 – General requirements.
§ 820.181 – Device master record.
§ 820.184 – Device history record.
§ 820.186 – Quality system record.
§ 820.198 – Complaint files.
Subpart N – Servicing
§ 820.200 – Servicing.
Subpart O – Statistical Techniques
§ 820.250 – Statistical techniques.
[Code of Federal Regulations]
[Title 21, Volume 8]
[Revised as of April 1, 2012]
[CITE: 21CFR820.72]
TITLE 2 – FOOD AND DRUGS
CHAPTER I – FOOD AND DRUG ADMINISTRATION
DEPARTMENT OF HEALTH AND HUMAN SERVICES
SUBCHAPTER H – MEDICAL DEVICES
14
quality standards and industry regulations
PART 820–QUALITY SYSTEM REGULATION
Subpart G–Production and Process Controls
Sec. 820.72 Inspection, measuring, and test equipment.
(a) Control of inspection, measuring, and test equipment. Each
manufacturer shall ensure that all inspection, measuring, and
test equipment, including mechanical, automated, or electronic
inspection and test equipment, is suitable for its intended purposes
and is capable of producing valid results. Each manufacturer shall
establish and maintain procedures to ensure that equipment is
routinely calibrated, inspected, checked, and maintained. The
procedures shall include provisions for handling, preservation,
and storage of equipment, so that its accuracy and fitness for use
are maintained. These activities shall be documented.
(b) C
alibration. Calibration procedures shall include specific directions
and limits for accuracy and precision. When accuracy and precision
limits are not met, there shall be provisions for remedial action to
reestablish the limits and to evaluate whether there was any adverse
effect on the device’s quality. These activities shall be documented.
(1) C
alibration standards. Calibration standards used for
inspection, measuring, and test equipment shall be traceable to
national or international standards. If national or international
standards are not practical or available, the manufacturer shall
use an independent reproducible standard. If no applicable
standard exists, the manufacturer shall establish and maintain
an in-house standard.
(2) C
alibration records. The equipment identification, calibration
dates, the individual performing each calibration, and the
next calibration date shall be documented. These records shall
be displayed on or near each piece of equipment or shall be
readily available to the personnel using such equipment and
to the individuals responsible for calibrating the equipment.
15
quality standards and industry regulations
[Code of Federal Regulations]
[Title 21, Volume 4]
[Revised as of April 1, 2012]
[CITE: 21CFR211]
TITLE 21 – FOOD AND DRUGS
CHAPTER I – FOOD AND DRUG ADMINISTRATION
DEPARTMENT OF HEALTH AND HUMAN SERVICES
SUBCHAPTER C – DRUGS: GENERAL
PART 211
CURRENT GOOD MANUFACTURING PRACTICE FOR
FINISHED PHARMACEUTICALS
Subpart D – Equipment
Sec. 211.68 Automatic, mechanical, and electronic equipment.
(a) Automatic, mechanical, or electronic equipment or other types
of equipment, including computers, or related systems that will
perform a function satisfactorily, may be used in the manufacture,
processing, packing, and holding of a drug product. If such
equipment is so used, it shall be routinely calibrated, inspected, or
checked according to a written program designed to assure proper
performance. Written records of those calibration checks and
inspections shall be maintained.
Sec. 211.160 General requirements.
(b) Laboratory controls shall include the establishment of scientifically
sound and appropriate specifications, standards, sampling plans,
and test procedures designed to assure that components, drug
product containers, closures, in-process materials, labeling, and
drug products conform to appropriate standards of identity,
strength, quality, and purity. Laboratory controls shall include:
(1) Determination of conformity to applicable written
specifications for the acceptance of each lot within each
shipment of components, drug product containers, closures,
16
quality standards and industry regulations
and labeling used in the manufacture, processing, packing,
or holding of drug products. The specifications shall include
a description of the sampling and testing procedures used.
Samples shall be representative and adequately identified.
Such procedures shall also require appropriate retesting of any
component, drug product container, or closure that is subject
to deterioration.
(2) Determination of conformance to written specifications and a
description of sampling and testing procedures for in-process
materials. Such samples shall be representative and properly
identified.
(3) Determination of conformance to written descriptions of
sampling procedures and appropriate specifications for drug
products. Such samples shall be representative and properly
identified.
(4) The calibration of instruments, apparatus, gauges, and
recording devices at suitable intervals in accordance with an
established written program containing specific directions,
schedules, limits for accuracy and precision, and provisions for
remedial action in the event accuracy and/or precision limits
are not met. Instruments, apparatus, gauges, and recording
devices not meeting established specifications shall not be
used.
[43 FR 45077, Sept. 29, 1978, as amended at 73 FR 51932,
Sept. 8, 2008]
Sec. 211.194 Laboratory records.
(d) Complete records shall be maintained of the periodic calibration
of laboratory instruments, apparatus, gauges, and recording
devices required by 211.160(b)(4).
17
quality standards and industry regulations
TITLE 2 – FOOD AND DRUGS
CHAPTER I – FOOD AND DRUG ADMINISTRATION
DEPARTMENT OF HEALTH AND HUMAN SERVICES
SUBCHAPTER A – GENERAL
PART 11
ELECTRONIC RECORDS; ELECTRONIC SIGNATURES
Subpart A – General Provisions
Sec. 11.1 Scope.
(a) The regulations in this part set forth the criteria under which
the agency considers electronic records, electronic signatures,
and handwritten signatures executed to electronic records to be
trustworthy, reliable, and generally equivalent to paper records
and handwritten signatures executed on paper.
(b) This part applies to records in electronic form that are created,
modified, maintained, archived, retrieved, or transmitted, under
any records requirements set forth in agency regulations. This
part also applies to electronic records submitted to the agency
under requirements of the Federal Food, Drug, and Cosmetic Act
and the Public Health Service Act, even if such records are not
specifically identified in agency regulations. However, this part
does not apply to paper records that are, or have been, transmitted
by electronic means.
(c) Where electronic signatures and their associated electronic records
meet the requirements of this part, the agency will consider
the electronic signatures to be equivalent to full handwritten
signatures, initials, and other general signings as required by
agency regulations, unless specifically excepted by regulation(s)
effective on or after August 20, 1997.
(d) Electronic records that meet the requirements of this part may be
used in lieu of paper records, in accordance with 11.2, unless paper
records are specifically required.
18
quality standards and industry regulations
(e) Computer systems (including hardware and software), controls, and
attendant documentation maintained under this part shall be readily
available for, and subject to, FDA inspection.
(f) This part does not apply to records required to be established or
maintained by 1.326 through 1.368 of this chapter. Records that
satisfy the requirements of part 1, subpart J of this chapter, but that
also are required under other applicable statutory provisions or
regulations, remain subject to this part.
[62 FR 13464, Mar. 20, 1997, as amended at 69 FR 71655,
Dec. 9, 2004]
Sec. 11.2 Implementation.
(a) For records required to be maintained but not submitted to the
agency, persons may use electronic records in lieu of paper records
or electronic signatures in lieu of traditional signatures, in whole or
in part, provided that the requirements of this part are met.
(b) For records submitted to the agency, persons may use electronic
records in lieu of paper records or electronic signatures in lieu of
traditional signatures, in whole or in part, provided that:
(1) The requirements of this part are met; and
(2) The document or parts of a document to be submitted have been
identified in public docket No. 92S-0251 as being the type of
submission the agency accepts in electronic form. This docket
will identify specifically what types of documents or parts of
documents are acceptable for submission in electronic form
without paper records and the agency receiving unit(s) (e.g.,
specific center, office, division, branch) to which such submissions
may be made. Documents to agency receiving unit(s) not specified
in the public docket will not be considered as official if they are
submitted in electronic form; paper forms of such documents
will be considered as official and must accompany any electronic
records. Persons are expected to consult with the intended agency
receiving unit for details on how (e.g., method of transmission,
media, file formats, and technical protocols) and whether to
proceed with the electronic submission.
19
quality standards and industry regulations
TITLE 21--FOOD AND DRUGS
CHAPTER I--FOOD AND DRUG ADMINISTRATION
DEPARTMENT OF HEALTH AND HUMAN SERVICES
SUBCHAPTER A--GENERAL
PART 11
ELECTRONIC RECORDS; ELECTRONIC SIGNATURES
Subpart C – Electronic Signatures
Sec. 11.100 General requirements.
(a) Each electronic signature shall be unique to one individual and
shall not be reused by, or reassigned to, anyone else.
(b) Before an organization establishes, assigns, certifies, or otherwise
sanctions an individual`s electronic signature, or any element of
such electronic signature, the organization shall verify the identity
of the individual.
(c) Persons using electronic signatures shall, prior to or at the time
of such use, certify to the agency that the electronic signatures
in their system, used on or after August 20, 1997, are intended
to be the legally binding equivalent of traditional handwritten
signatures.
(1) The certification shall be submitted in paper form and signed
with a traditional handwritten signature, to the Office of
Regional Operations (HFC-100), 12420 Parklawn Drive, RM
3007 Rockville, MD 20857.
(2) Persons using electronic signatures shall, upon agency request,
provide additional certification or testimony that a specific
electronic signature is the legally binding equivalent of the
signer`s handwritten signature.
20
quality standards and industry regulations
Calibration requirements according to the European Medicines
Agency (EMA)
Following are examples of some of the regulatory requirements of
the EMA, and what they say about calibration and what must be
accomplished to meet the GMPs.
Eudralex Volume 4
Chapter 3: Premises and Equipment
Equipment
3.41 Measuring, weighing, recording and control equipment should be
calibrated and checked at defined intervals by appropriate methods.
Adequate records of such tests should be maintained.
Chapter 4: Documentation
Manufacturing Formula and Processing Instructions
Approved, written Manufacturing Formula and Processing
Instructions should exist for each product and batch size to be
manufactured.
4.18 The Processing Instructions should include:
a) A statement of the processing location and the principal equipment
to be used; b) The methods, or reference to the methods, to be used for
preparing the critical equipment (e.g. cleaning, assembling, calibrating,
sterilising); c) Checks that the equipment and work station are clear
of previous products, documents or materials not required for the
planned process, and that equipment is clean and suitable for use; d)
Detailed stepwise processing instructions [e.g. checks on materials,
pre-treatments, sequence for adding materials, critical process
parameters (time, temp etc)]; e) The instructions for any in-process
controls with their limits; f ) Where necessary, the requirements for
bulk storage of the products; including the container, labeling and
special storage conditions where applicable; g) Any special precautions
to be observed.
21
quality standards and industry regulations
Procedures and records
Other
4.29 There should be written policies, procedures, protocols, reports
and the associated records of actions taken or conclusions reached,
where appropriate, for the following examples:
• Validation and qualification of processes, equipment and systems;
• Equipment assembly and calibration;
• Technology transfer;
• Maintenance, cleaning and sanitation;
• Personnel matters including signature lists, training in GMP and
technical matters, clothing and hygiene and verification of the
effectiveness of training.
• Environmental monitoring;
• Pest control;
• Complaints;
• Recalls;
• Returns;
• Change control;
• Investigations into deviations and non-conformances;
• Internal quality/GMP compliance audits;
• Summaries of records where appropriate
(e.g. product quality review);
• Supplier audits.
4.31 Logbooks should be kept for major or critical analytical testing,
production equipment, and areas where product has been processed.
They should be used to record in chronological order, as appropriate,
any use of the area, equipment/method, calibrations, maintenance,
cleaning or repair operations, including the dates and identity of
people who carried these operations out.
22
quality standards and industry regulations
Chapter 6 Quality Control
Good Quality Control Laboratory Practice
Documentation
6.7 Laboratory documentation should follow the principles given
in Chapter 4. An important part of this documentation deals with
Quality Control and the following details should be readily available
to the Quality Control Department:
• specifications;
• sampling procedures;
• testing procedures and records (including analytical worksheets and/
or laboratory notebooks);
• analytical reports and/or certificates;
• data from environmental monitoring, where required;
• validation records of test methods, where applicable;
• procedures for and records of the calibration of instruments and
maintenance of equipment.
Annex 15 to the EU Guide to Good Manufacturing Practice
Title: Qualification and validation
QUALIFICATION
Installation qualification
11. Installation qualification (IQ ) should be performed on new or
modified facilities, systems and equipment.
12. IQ should include, but not be limited to the following:
(a) installation of equipment, piping, services and instrumentation
checked to current engineering drawings and specifications;
(b) icollection and collation of supplier operating and working
instructions and maintenance requirements;
(c) icalibration requirements;
(d) verification of materials of construction.
23
quality standards and industry regulations
Operational qualification
15. The completion of a successful Operational qualification
should allow the finalisation of calibration, operating and cleaning
procedures, operator training and preventative maintenance
requirements. It should permit a formal “release” of the facilities,
systems and equipment.
Qualification of established (in-use) facilities, systems and equipment
19. Evidence should be available to support and verify the operating
parameters and limits for the critical variables of the operating
equipment. Additionally, the calibration, cleaning, preventative
maintenance, operating procedures and operator training procedures
and records should be documented.
PROCESS VALIDATION
Prospective validation
24. Prospective validation should include, but not be limited to the
following:
(a) short description of the process;
(b) summary of the critical processing steps to be investigated;
(c) list of the equipment/facilities to be used (including measuring/
monitoring/recording equipment) together with its calibration
status
(d) finished product specifications for release;
(e) list of analytical methods, as appropriate;
(f) proposed in-process controls with acceptance criteria;
(g) additional testing to be carried out, with acceptance criteria and
analytical validation, as appropriate;
(h) sampling plan;
(i) methods for recording and evaluating results
(j) functions and responsibilities;
(k) proposed timetable.
24
quality standards and industry regulations
EU GMP Annex 11
The EU GMP Annex 11 defines EU requirements for computerised
systems, and applies to all forms of computerised systems used as part
of GMP regulated activities.
Main page for the EudraLex - Volume 4 Good manufacturing practice
(GMP) Guidelines:
http://ec.europa.eu/health/documents/eudralex/vol-4/index_en.htm
PDF of Annex 11:
http://ec.europa.eu/health/files/eudralex/vol-4/annex11_01-2011_
en.pdf
EUROPEAN COMMISSION
HEALTH AND CONSUMERS DIRECTORATE-GENERAL
Public Health and Risk Assessment
Pharmaceuticals
Brussels,
SANCO/C8/AM/sl/ares(2010)1064599
EudraLex
The Rules Governing Medicinal Products in the European Union
Volume 4
Good Manufacturing Practice
Medicinal Products for Human and Veterinary Use
Annex 11: Computerised Systems
Legal basis for publishing the detailed guidelines: Article 47 of Directive
2001/83/EC on the Community code relating to medicinal products
for human use and Article 51 of Directive 2001/82/EC on the
Community code relating to veterinary medicinal products. This
document provides guidance for the interpretation of the principles
25
quality standards and industry regulations
and guidelines of good manufacturing practice (GMP) for medicinal
products as laid down in Directive 2003/94/EC for medicinal products
for human use and Directive 91/412/EEC for veterinary use. Status of
the document: revision 1
Reasons for changes: the Annex has been revised in response to the
increased use of computerised systems and the increased complexity
of these systems. Consequential amendments are also proposed for
Chapter 4 of the GMP Guide.
Deadline for coming into operation: 30 June 2011
Commission Européenne, B-1049 Bruxelles / Europese Commissie,
B-1049 Brussel - Belgium
Telephone: (32-2) 299 11 11
Principle
This annex applies to all forms of computerised systems used as
part of a GMP regulated activities. A computerised system is a set
of software and hardware components which together fulfill certain
functionalities.
The application should be validated; IT infrastructure should be
qualified.
Where a computerised system replaces a manual operation, there
should be no resultant decrease in product quality, process control or
quality assurance. There should be no increase in the overall risk of
the process.
PIC/S
The abbreviation PIC/S describes both the Pharmaceutical Inspection
Convention (PIC) and the Pharmaceutical Inspection Co-operation
Scheme (PIC Scheme) which operate together. It aims to promote
harmonisation of global regulations for the pharmaceutical industry.
Further information can be found at the PIC/S Web site (http://www.
picscheme.org/.).
26
quality standards and industry regulations
GAMP®
GAMP® is a Community of Practice (COP) of the International
Society for Pharmaceutical Engineering (ISPE). The GAMP® COP
aims to provide guidance and understanding concerning GxP
computerized systems. COPs provide networking opportunities
for people interested in similar topics. The GAMP® COP organizes
discussion forums for its members and ISPE organises GAMP® related
training courses and educational seminars.
GAMP® itself was founded in 1991 in the United Kingdom to
deal with the evolving FDA expectations for Good Manufacturing
Practice (GMP) compliance of manufacturing and related systems.
Since 1994, the organization entered into a partnership with the ISPE
and published its first GAMP® guidelines.
Three regional Steering Committees, GAMP® Japan, GAMP®
Europe, and GAMP® Americas support the GAMP® Council which
oversee the operation of the COP and is the main link to ISPE.
Several local GAMP® COPs, such as GAMP® Americas, GAMP®
Nordic, GAMP® DACH (Germany, Austria, Switzerland), GAMP®
Francophone, GAMP® Italiano and GAMP® Japan, produce technical
content and translate ISPE technical documents. They also bring the
GAMP® community closer to its members, in collaboration with
ISPE’s local Affiliates in these regions.
The most well known GAMP® publication is GAMP ® 5 A RiskBased Approach to GxP Computerized Systems. This is the latest major
revision and was released in January 2008. There is also a series of
related GAMP® guidance on specific topics, including:
• GAMP ® Good Practice Guide: A Risk-Based Approach to
Calibration Management (Second Edition)
• GAMP® Good Practice Guide: A Risk-Based Approach to GxP
Compliant Laboratory Computerized Systems (Second Edition)
• GAMP® Good Practice Guide: A Risk-Based Approach to GxP
Process Control Systems (Second Edition)
• GAMP® Good Practice Guide: A Risk-Based Approach to Operation
of GxP Computerized Systems - A Companion Volume to GAMP® 5
• GAMP® Good Practice Guide: Electronic Data Archiving
• GAMP® Good Practice Guide: Global Information Systems Control
and Compliance
27
quality standards and industry regulations
• GAMP® Good Practice Guide: IT Infrastructure Control and
Compliance
• GAMP® Good Practice Guide: Legacy Systems
The GAMP® Good Practice Guide: A Risk-Based Approach to
Calibration Management (second edition) was developed by ISPE’s
GAMP® COP Calibration Special Interest Group (SIG) in conjunction
with representatives from the pharmaceutical industry and input from
regulatory agencies. The Guide describes the principles of calibration
and presents guidance in setting up a calibration management system,
providing a structured approach to instrument risk assessment,
calibration program management, documentation, and corrective
actions vital to regulatory compliance. The second edition of the guide
has been significantly updated to address the change in regulatory
expectations and in associated industry guidance documents. The
scope now includes related industries, laboratory, and analytical
instrumentation. A set of associated attachments are also available
through the ISPE website.
ISO 9001:2008
Basically, this is what is required according to ISO 9001:2008
7.6 CONTROL MONITORING AND MEASURING
EQUIPMENT
• Identify your organization’s monitoring and measuring needs
and requirements (if your test instrument makes a quantitative
measurement, it requires periodic calibration); and select test
equipment that can meet those monitoring and measuring needs
and requirements. 
• Establish monitoring and measuring processes (calibration
procedures and calibration record templates for recording your
calibration results). 
• Calibrate your monitoring and measuring equipment using a period
schedule to ensure that results are valid (you should also perform
a yearly evaluation of your calibration results to see if there is a
need to increase or decrease your calibration intervals on calibrated
test equipment). All calibrations must be traceable to a national or
international standard or artifact. 
28
quality standards and industry regulations
• Protect your monitoring and measuring equipment (this includes
during handling, preservation, storage, transportation, and shipping
of all test instruments – to include your customer’s items, and your
calibration standards). 
• Confirm that monitoring and measuring software is capable of
doing the job you want it to do (your software needs to be validated
before being used, and when required, your test instruments may
need to be qualified prior to use). 
• Evaluate the validity of previous measurements whenever you
discover that your measuring or monitoring equipment is out-ofcalibration (as stated in the FDA regulations, “When accuracy and
precision limits are not met, there shall be provisions for remedial
action to reestablish the limits and to evaluate whether there was
any adverse effect on the device’s quality”; this is just as applicable
when dealing with ISO as with any other standard or regulation;
especially when the out of tolerance item is a calibration standard,
and may have affected numerous items of test equipment over a
period of time).
ISO 17025
ISO 17025 – General requirements for the competence of testing and
calibration laboratories. According to ISO 17025, this standard is
applicable to all organizations performing tests and/or calibrations.
These include first-, second-, and third-party laboratories, and
laboratories where testing and/or calibration forms part of inspection
and product certifications. Please keep in mind that if your calibration
function and/or metrology department fall under the requirements
of your company, rather it be for compliance to an ISO standard
(ISO 9001:2008 or ISO 13485) or an FDA requirement (cGMP, QSR,
etc.), then you do not have any obligation to meet the ISO 17025
standard. You already fall under a quality system that takes care of
your calibration requirements.
ANSI/NCSL Z540.3-2006
ANSI/NCSL Z540.3-2006 – American National Standard for
Calibration-Requirements for the Calibration of Measuring and Test
Equipment.
29
quality standards and industry regulations
The objective of this National Standard is to establish the technical
requirements for the calibration of measuring and test equipment.
This is done through the use of a system of functional components.
Collectively, these components are used to manage and assure that
the accuracy and reliability of the measuring and test equipment are
in accordance with identified performance requirements.
In implementing its objective, this National Standard describes the
technical requirements for establishing and maintaining:
• the acceptability of the performance of measuring and test
equipment;
• the suitability of a calibration for its intended application;
• the compatibility of measurements with the National Measurement
System; and
• the traceability of measurement results to the International System
of Units (SI).
In the development of this National Standard attention has been
given to:
• expressing the technical requirements for a calibration system
supporting both government and industry needs;
• applying best practices and experience with related national,
international, industry, and government standards; and
• balancing the needs and interests of all stakeholders.
In addition, this National Standard includes and updates the relevant
calibration system requirements for measuring and test equipment
described by the previous standards, Part 11 of ANSI/NCSL Z540.1
(R2002) and Military Standard 45662A.
This National Standard is written for both Supplier and Customer,
each term being interpreted in the broadest sense. The “Supplier may
be a producer, distributor, vendor, or a provider of a product, service,
or information. The “Customer” may be a consumer, client, enduser,
retailer, or purchaser that receives a product or service.
Reference to this National Standard may be made by:
• customers when specifying products (including services) required;
• suppliers when specifying products offered;
• legislative or regulatory bodies;
• agencies or organizations as a contractual condition for
procurement; and
• assessment organizations in the audit, certification, and other
evaluations of calibration systems and their components.
30
quality standards and industry regulations
This National Standard is specific to calibration systems. A
calibration system operating in full compliance with this National
Standard promotes confidence and facilitates management of the risks
associated with measurements, tests, and calibrations.8
Equipment intended for use in potentially explosive atmospheres
(ATEX)
What are ATEX and IECEx?
ATEX (“ATmosphères EXplosibles”, explosive atmospheres in French)
is a standard set in the European Union for explosion protection in the
industry. ATEX 95 equipment directive 94/9/EC concerns equipment
intended for use in potentially explosive areas. Companies in the
EU where the risk of explosion is evident must also use the ATEX
guidelines for protecting the employees. In addition, the ATEX rules
are obligatory for electronic and electrical equipment that will be used
in potentially explosive atmospheres sold in the EU as of July 1, 2003.
IEC (International Electrotechnical Commission) is a nonprofit
international standards organization that prepares and publishes
International Standards for electrical technologies. The IEC TC/31
technical committee deals with the standards related to equipment for
explosive atmospheres. IECEx is an international scheme for certifying
procedures for equipment designed for use in explosive atmospheres.
The objective of the IECEx Scheme is to facilitate international trade
in equipment and services for use in explosive atmospheres, while
maintaining the required level of safety.
In most cases, test equipment that is required to be operated in
an explosive environment would be qualified and installed by the
company’s facility services department and not the calibration
personnel. One must also keep in mind that there would be two
different avenues for the calibration of those pieces of test equipment:
on-site and off-site. If the test instrument that is used in an explosive
environment must be calibrated on-site (in the explosive environment),
then all the standards used for that calibration must also comply
with explosive environment directives. However, if it were possible
to remove the test equipment from the explosive environment when
due for their period calibration, then there would be no requirement
for the standards used for their calibration to meet the explosive
31
quality standards and industry regulations
environment directives, saving money on expensive standards and
possibly expensive training of calibration personnel in order for them
to work in those conditions.
Having said that, there may be a need for the calibration personnel
to be aware of the ATEX regulations. An informative website for
information on ATEX can be found by typing in the following link:
http://ec.europa.eu/enterprise/atex/indexinfor.htm. Several languages
are available for retrieving the information.
Another informative website is the International Electrotechnical
Commission Scheme for Certification to Standards Relating to
Equipment for use in Explosive Atmospheres (IECEx Scheme). The
link is: http://www.iecex.com/guides.htm.
1. Bucher, Jay L. 2007. The Quality Calibration Handbook.
Milwaukee: ASQ Quality Press.
2. The Story of the Egyptian Cubit. http://www.ncsli.org/misc/
cubit.cfm. (18 October, 2008)
3. 21CFR Part 211.68, 211.160: http://www.accessdata.fda.gov/
scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPart=211/
(5 July, 2012)
4. 21CFR Part 11. http://www.fda.gov/downloads/
RegulatoryInformation/Guidances/ucm125125.pdf (5 July, 2012)
and http://www.fda.gov/RegulatoryInformation/Guidances/
ucm125067.htm?utm_campaign=Google2&utm_
source=fdaSearch&utm_medium=website&utm_term=21 CFR
part 11&utm_content=3
5. GAMP. http://en.wikipedia.org/wiki/Good_Automated_
Manufacturing_Practice (5 July, 2012)
6. NCSL International. 2006. ANSI/NCSL Z540.3-2006.
Boulder, CO.
32
34
a basic quality calibration program
A basic quality
calibration program
R
&D departments are tasked with coming up with the answers
to many problems; the cure for cancer is one of them. Let’s
imagine that the Acme Biotech Co. has found the cure for
cancer. Their R&D section sends the formula to their operations &
manufacturing division. The cure cannot be replicated with consistent
results. They are not using calibrated test instruments in the company.
Measurements made by R&D are different than those made by the
operations section. If all test equipment were calibrated to a traceable
standard, then repeatable results would ensure that what’s made in one
part of the company is also repeated in another part of the company.
The company loses time, money, their reputation, and possibly the
ability to stay in business simply because they do not use calibrated
test equipment. A fairy tale? Not hardly. This scenario is repeated
every day throughout the world.
Without calibration, or by using incorrect calibrations, all of us pay
more at the gas pump, for food weighed incorrectly at the checkout
counter, and for manufactured goods that do not meet their stated
specifications. Incorrect amounts of ingredients in your prescription
and over-the-counter (OTC) drugs can cost more, or even cause
illness or death. Because of poor or incorrect calibration, criminals
are either not convicted or are released on bad evidence. Crime labs
cannot identify the remains of victims or wrongly identify victims
in the case of mass graves. Airliners fly into mountaintops and off
the ends of runways because they don’t know their altitude and/or
speed. Babies are not correctly weighed at birth. The amount of drugs
confiscated in a raid determines whether the offense is a misdemeanor
or a felony; which weight is correct? As one can see, having the correct
measurements throughout any and all industries is critical to national
and international trade and commerce.
35
a basic quality calibration program
The bottom line is this – all test equipment that make a quantitative
measurement require periodic calibration. It is as simple as that.
However, before we go any further, we need to clarify two definitions
that are critical to this subject – calibration and traceability.
By definition:
Calibration is a comparison of two measurement devices or systems,
one of known uncertainty (your standard) and one of unknown
uncertainty (your test equipment or instrument).
Traceability is the property of the result of a measurement or the value
of a standard whereby it can be related to stated references, usually
national or international standards, through an unbroken chain of
calibrations all having stated uncertainties.
The calibration of any piece of equipment or system is simply
a comparison between the standard being used (with its known
uncertainty), and the unit under test (UUT) or test instrument that
is being calibrated (the uncertainty is unknown, and that is why it is
being calibrated). It does not make any difference if you adjust, align or
repair the item, nor if you cannot adjust or align it. The comparison to
a standard that is more accurate, no matter the circumstances is called
calibration. Many people are under the misconception that an item
must be adjusted or aligned in order to be calibrated. Nothing could
be further from the truth.
Before we can get any deeper into what traceability is, we should
explain two different traceability pyramids. When we talk about
traceability to a national or international standard, the ‘everyday
calibration technician’ is usually situated close to the bottom of the
pyramid, so a graphic illustration of these pyramids is important.
The two examples in figures 1 and 2 are similar, but differ depending
on where you are in the chain, or certain parts of the world.
There are basically two ways to maintain traceability during
calibration – the use of an uncertainty budget (performing uncertainty
calculations for each measurement); and using a test uncertainty ratio
(TUR) of ≥ 4:1. First, let’s discuss the use of uncertainty budgets.
According to the European cooperation for Accreditation of
Laboratories, publication reference (EAL-G12) Traceability of Measuring
and Test Equipment to National Standards; the purpose of which is to
give guidance on the calibration and maintenance of measuring
36
a basic quality calibration program
BIPM
NMIs
Reference standards
Working metrology labs
General purpose calibration labs
(inside a company)
User’s test equipment
Figure 1
SI units
Primary stds.
Secondary standards
Reference standards
Working standards
User’s test equipment
Figure 2
Note: NMI = National Metrology Institute
equipment in meeting the requirements of the ISO 9000 series of
standards for quality systems, and the EN 45001 standard for the
operation of testing laboratories; paragraphs 4 and 5 are very specific
in their requirements:
4 Why are calibrations and traceability necessary?
4.1 Traceability of measuring and test equipment to national standards
by means of calibration is necessitated by the growing national and
international demand that manufactured parts be interchangeable;
supplier firms that make products, and customers who install them
with other parts, must measure with the ‘same measure’.
37
a basic quality calibration program
4.2 There are legal as well as technical reasons for traceability of
measurement. Relevant laws and regulations have to be complied
with just as much as the contractual provisions agreed with the
purchaser of the product (guarantee of product quality) and the
obligation to put into circulation only products whose safety, if
they are used properly, is not affected by defects.
Note: If binding requirements for the accuracy of measuring
and test equipment have been stipulated, failure to meet these
requirements means the absence of a warranted quality with
considerable consequent liability.
4.3 If it becomes necessary to prove absence of liability, the producer
must be able to demonstrate, by reference to a systematic and fully
documented system, that adequate measuring and test equipment
was chosen, was in proper working order and was used correctly
for controlling a product.
4.4 There are similar technical and legal reasons why calibration and
testing laboratory operators should have consistent control of
measuring and test equipment in the manner described.
5 Elements of traceability
5.1 Traceability is characterised by a number of essential elements:
(a) an unbroken chain of comparisons going back to a standard
acceptable to the parties, usually a national or international
standard;
(b) measurement uncertainty; the measurement uncertainty
for each step in the traceability chain must be calculated
according to agreed methods and must be stated so that an
overall uncertainty for the whole chain may be calculated;
(c) documentation; each step in the chain must be performed
according to documented and generally acknowledged
procedures; the results must equally be documented;
(d) competence; the laboratories or bodies performing one or
more steps in the chain must supply evidence for their technical
competence, e.g. by demonstrating that they are accredited;
(e) reference to SI units; the chain of comparisons must end at
primary standards for the realization of the SI units;
(f) re-calibrations; calibrations must be repeated at appropriate
intervals; the length of these intervals will depend on a number
of variables, e.g. uncertainty required, frequency of use, way of
use, stability of the equipment.
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a basic quality calibration program
5.2 In many fields, reference materials take the position of physical
reference standards. It is equally important that such reference
materials are traceable to relevant SI units. Certification of
reference materials is a method that is often used to demonstrate
traceability to SI units.1
The other document that goes hand-in-hand with this is EA 4/02,
Expression of the Uncertainty of Measurement in Calibration. The
purpose of this document is to harmonise evaluation of uncertainty
of measurement within EA, to set up, in addition to the general
requirements of EAL-R1, the specific demands in reporting
uncertainty of measurement on calibration certificates issued by
accredited laboratories and to assist accreditation bodies with a
coherent assignment of best measurement capability to calibration
laboratories accredited by them. As the rules laid down in this
document are in compliance with the recommendations of the Guide
to the Expression of Uncertainty in Measurement, published by
seven international organisations concerned with standardisation and
metrology, the implementation of EA-4/02 will also foster the global
acceptance of European results of measurement.2
By understanding and following both of these documents, a
calibration function can easily maintain traceable calibrations for
the requirements demanded by their customers and the standard or
regulation that their company needs to meet.
To maintain traceability, without using uncertainty budgets or
calculations, you must ensure your standards are at least four times
(4:1) more accurate than the test equipment being calibrated. Where
does this ratio of four to one (4:1) come from? It comes from the
American National Standard for Calibration – (ANSI/NCSL Z540.32006) which states: “Where calibrations provide for verification that
measurement quantities are within specified tolerances…Where it is not
practical to estimate this probability, the TUR shall be equal to or greater
than 4:1.”
So, if a TUR of equal to or greater than 4:1 is maintained, then
traceability is assured. Keep in mind that a TUR of 4:1 somewhere
along the chain of calibrations may not have been feasible, and
uncertainty calculations were performed and their uncertainty stated
on the certificate of calibration. This is correct and acceptable. In
most circumstances, where the need to maintain a TUR of 4:1 comes
into play, is at the company or shop level, where the customer’s test
39
a basic quality calibration program
equipment is usually used for production or manufacturing purposes
only.
So how does calibration and traceability fit into the big picture?
What does the big picture look like? Why do you need a quality
calibration program?
You need to establish a quality calibration program to ensure that
all operations throughout the metrology department occur in a stable
manner. The effective operation of such a system will hopefully result
in stable processes and, therefore, in a consistent output from those
processes. Once stability and consistency are achieved, it is possible
to initiate process improvements. This is applicable in every phase of
a production and/or manufacturing program. But especially true in a
metrology department.3
Let’s take for example a calibration program that has six calibration
technicians on staff. Four of them work in another facility calibrating
the same types of equipment as the other two. However, the other two
have far more experience and through no fault of their own do not use
the calibration procedures that are required by their quality system.
They have calibrated the same items for several years and feel there is
nothing new to learn. One of the four calibration technicians (who
are always following the calibration procedures) finds there is a fast,
more economical way to perform a specific calibration. They submit a
change proposal for the calibration procedure and everyone is briefed
and trained on the new technique. The four calibration technicians
that have been following the calibration procedure improve their
production and save the company money. The two ‘old timers’ have a
reduction in their production and actually cost the company money. If
everyone was using the calibration procedures like they were supposed
to, then this would not have happened.
Process improvements cannot take place across the department if
everyone is not doing the job the same way each and every time they
perform a calibration.
We are not ignorant enough to believe that when calibration
technicians have performed a particular calibration hundreds or even
thousands of times that they are going to follow calibration procedures
word for word. Of course not. But they must have their calibration
procedure on hand each time they are performing the calibration. If
a change has been made to that procedure, the calibration technician
must be trained on the change before they can perform the calibration;
and the appropriate documentation completed to show that training
40
a basic quality calibration program
was accomplished and signed off. When the proper training is not
documented and signed off by the trainer and trainee, then it is the
same as if the training never happened.
What is a quality calibration program?
A quality calibration program consists of several broad items referred
to in the Quality System Regulation (QSR) from the Food and Drug
Administration (FDA). These items are also referred to by other
standards (ISO 9000, etc.) and regulations throughout most industries
that regulate or monitor production and manufacturing of all types
of products. One of the most stringent requirements can be found in
the current Good Manufacturing Procedures (GMP).
The basic premise and foundation of a quality calibration program
is to “Say what you do, Do what you say, Record what you did, Check the
results, and Act on the difference”. Let’s break these down into simple
terms.
“Say what you do” means write in detail how to do your job. This
includes calibration procedures, work instructions and standard
operating procedures (SOPs).
“Do what you say” means follow the documented procedures or
instructions every time you calibrate, or perform a function that
follows specific written instructions.
“Record what you did” means that you must record the results of your
measurements and adjustments, including what your standard(s) read or
indicated both before and after any adjustments might be made.
“Check the results” means make certain the test equipment meets
the tolerances, accuracies, or upper/lower limits specified in your
procedures or instructions.
“Act on the difference” means if the test equipment is out of tolerance,
you’re required to inform the user/owner of the equipment because
they may have to re-evaluate manufactured goods, change a process,
or recall a product.3
“Say what you do” means write in detail how to do your job. This
includes calibration procedures, work instructions and SOPs. All
of your calibration procedures should be formatted the same as
other SOPs within your company. Here is an example of common
formatting for SOPs:
41
a basic quality calibration program
1.
2.
3.
4.
5.
6.
7.
8.
Procedures
Scope
Responsibilities
Definitions
Procedure
Related Procedures
Forms and Records
Document History
After section 4. Definitions, you should have a table listing all of the
instruments or systems that would be calibrated by that procedure,
along with their range and tolerances. After that you should have a
list of the standards to be used to calibrate the items. This table should
also include the standard’s range and specifications. Then the actual
calibration procedure starts in section 5. Procedures.
Manufacturer’s manuals usually provide an alignment procedure
that can be used as a template for writing a calibration procedure. They
should show what standards accomplish the calibration of a specific
range and/or function. A complete calibration must be performed
prior to any adjustment or alignment. An alignment procedure and/
or preventive maintenance inspection (PMI) may be incorporated
into your SOP as long as it is separate from the actual calibration
procedure.
There are, generally speaking, two types of calibration procedures:
Generic: temperature gages and thermometers, pressure and vacuum
gages, pipettes, micrometers, power supplies and water baths.
Specific: spectrophotometers, thermal cyclers, and balances/scales.
Generic SOPs are written to show how to calibrate a large variety
of items in a general context. Specific SOPs are written to show stepby-step procedures for each different type of test instrument within
a group of items. Possibly, the calibration form is designed to follow
specific steps (number wise); and removes doubt by the calibration
technician on what data goes into which data field.
“Do what you say” means follow the documented procedures or
instructions every time you calibrate, or perform a function that follows
specific written instructions. This means following published calibration
procedures every time you calibrate a piece of test equipment.
Have the latest edition of the procedure available for use by your
calibration technicians. Have a system in place for updating your
42
a basic quality calibration program
procedures. Train your technicians on the changes made to your
procedures every time the procedure is changed or improved – and
document the training.
What do you do when you need to make an improvement, or update
your calibration procedures and/or forms? A formal, written process
must be in place, to include:
• Who can make changes
• Who is the final approval authority
• A revision tracking system
• A process for validating the changes
• An archiving system for old procedures
• Instructions for posting new/removal of old procedures
• A system for training on revisions
• A place to document that training was done
“Record what you did” means that you must record the results of your
measurements and adjustments, including what your standard(s) read
or indicated both before and after any adjustments are made, and keep
your calibration records in a secure location. Certain requirements
must be documented in each calibration record. Of course there are
many ways to accomplish this, including:
• pen and paper
• “do-it-yourself ” databases, e.g. Excel, Access
• calibration module of a computerized maintenance management
system (CMMS)
• calibration software specifically designed for that purpose
These include the identification of the test instrument with a unique
identification number, their part number and range/tolerance. The
location of where the test instrument can be found should also be on
the record. A history of each calibration and a traceability statement
or uncertainty budget must be included. The date of calibration, the
last time it was calibrated, and the next time it will be due calibration
should be on the form. There should be a place to show what the
standard read, as well as the test instrument’s ‘As Found’ and when
applicable ‘As Left’ readings.
The ‘As Found’ readings are what the test instrument read the first time
that a calibration is performed, prior to alignment, adjustment or repair.
The entire calibration is performed to see any part of the calibration
is out of tolerance. If an out-of-tolerance (OOT) condition is found,
43
a basic quality calibration program
record the reading (on the standard and the UUT) and continue with
the rest of the calibration to the end of the calibration procedure. If one
were to stop at the point where an OOT is found, make an adjustment,
then proceed with the calibration, there is a good possibility that the
adjustment affected other ranges or parts of the calibration. This is why
the entire calibration is performed prior to adjustment or alignment.
There will be times when an instrument has a catastrophic failure.
It just dies and cannot be calibrated. This should be noted in the
calibration record. Then, once the problem is found and repaired, an
‘As Found’ calibration is performed. The UUT is treated the same as
any OOT unit, but you would not have been able to collect the original
“As Found’ readings.
“As Left” readings are taken after repair, alignment, or adjustment.
Not all UUTs would be considered OOT when “As Left’ readings
are taken. In some circumstances, it might be metrology department
policy to adjust an item if it is more than ½ beyond its in-tolerance
range, while still meeting its specifications. In this type of situation,
after the UUT is adjusted to be as close to optimum as possible, a
complete calibration is again performed, collecting the ‘As Left’
readings for the final calibration record. Another example would be
when preventive maintenance inspection is going to be performed on
an item. The calibration is performed, collecting the ‘As Found’ data.
Then the PMI is completed, and an ‘As Left’ set of data is collected.
If the item is found to be out-of-tolerance at that time, there would
not be a problem since it was found to be in tolerance during the first
calibration. It would be obvious that something happened during the
cleaning, alignment or adjustment and that after a final adjustment
was completed to bring the unit back into tolerance, a final ‘As Left’
calibration would be performed.
The standard reading, from the working or reference standard you are
using to calibrate the UUT, will also be recorded on the calibration form.
Usually, the standard is set at a predetermined output, and the UUT is
read to see how much it deviates from the standard. This is a best practice
policy that has been in use in the metrology community since calibration
started. However, there will be times when this is not possible.
One example when it would not be practical to set the standard and
take a reading is during the calibration of water baths. The water bath
is set to a predetermined temperature, and the temperature standard is
used to record the actual reading. Compare this to the calibration of
pressure gages where a pressure standard is set to a standard pressure,
44
a basic quality calibration program
and the gage(s) under test are then read, and their pressures recorded on
the calibration record, and compared to the standard to see if they are
in or out of tolerance. In other case, just as the calibration of autoclaves,
they are set to complete a sterilization cycle and a temperature device
records all of the temperature readings throughout the cycle and the
readings are checked to see if the autoclave met its specifications. The
same happens when calibrating thermometers. They, along with the
standard, are placed in a dry block and a particular temperature is
set. The UUT is compared to the reference after equilibration, and a
determination is made as to the in or out of tolerance of the UUT. As
can be seen by the above examples, it is not always possible to set the
standard and take a reading from the UUT.
Also on the calibration form should be an area to identify the
standard(s) that were used, along with their next calibration due
date(s), plus their specifications and range.
There should also be a place to identify which calibration procedure
was used, along with the procedure’s revision number. There must be
a statement showing traceability to your NMI, or in the case of most
companies in the USA, to NIST, or to any artifact that was used as a
standard.
You should include any uncertainty budgets if used, or at least a
statement that a TUR of ≥ 4:1 was met.
List environment conditions when appropriate and show if they pass
or fail. According to NCSL International Calibration Control Systems
for the Biomedical and Pharmaceutical Industry – Recommended
Practice RP-6, paragraph 5.11: “The calibration environment need be
controlled only to the extent required by the most environmentally
sensitive measurement performed in the area.”4
According to ANSI/NCSL Z540.3-2006, paragraph 5.3.6 Influence
factors and conditions: “All factors and conditions of the calibration
area that adversely influence the calibration results shall be defined,
monitored, recorded, and mitigated to meet calibration process
requirements. Note: Influencing factors and conditions may include
temperature, humidity, vibration, electromagnetic interference, dust,
etc. Calibration shall be stopped when the adverse effects of the
influence factors ad conditions jeopardize the results of the calibration.”5
If the conditions within the area that calibrations are being performed
require monitoring according to the standard or requirements that must
be met, then a formal program must be in place for tracking those
conditions and reviewing the data. If this is the case, then there should
be a place in the calibration form for showing that those conditions were
45
a basic quality calibration program
either met, were not met, or are not applicable to that calibration.
You should indicate on the form if the calibration passed or failed.
If the UUT had an out-of-tolerance condition, then there should
be a place to show what happened to the UUT, with the following
possibilities as an example: 
• The user/customer was notified and the UUT was adjusted
and meets specifications.
• The user/customer was notified and the UUT was given
a ‘limited calibration’ with their written approval.
• The user/customer was notified and the UUT was taken
out of service and tagged as unusable.
Notice that in each circumstance that the user/customer must be
notified of any and all OOTs. This is called for in all of the standards
and regulations. The user/customer, even if internal to the company
performing the calibrations, must be informed if their test equipment
does not meet their specifications.
There should be an area set aside in the calibration form for making
comments or remarks. Enough space should be available for the
calibration technician to include information about the calibration,
OOT conditions, what was accomplished if an OOT was found, etc.
And finally, the calibration record must be signed and dated by
the technician performing the calibration. In some instances, the
calibration record requires a ‘second set of eyes’. This means that an
individual higher up the chain of command (supervisor, manager,
QA inspector, etc.) must review the calibration record and also sign
and date that it has been reviewed, audited, or inspected before it is
considered a completed record. If this is the case, there should be a
place on the form for the final reviewer to sign and date.
What do you do if, after recording your results, you find that you
have made an error, or transposed the wrong numbers, and want to
correct the error? For hard copy records, draw a single line through
the entry, write the correct data, and then place your initials and date
next to the data using black ink. Do not use white-out, or erase the
original data. For making corrections to electronic records (eRecords),
use whatever tracking system the software uses; or make a duplicate
record from scratch with the correct data and explain in the comments
block what happened, and date and sign accordingly.
There should be only one way to file your records, both hard copy
46
a basic quality calibration program
and eRecords – no matter which system you use, put it into your
written procedures.
An example for filing hard copy records:
• Each record is filed by its unique ID number
• Records are filed with the newest in the front
• Records are filed within a specified time frame
An example for filing eRecords:
• Filed by ID number, calibration certificate number and calibration
date
• Placed on a secure drive that has regular backup
• eRecords are filed within a specified time frame
There are many different ways to manage your calibration data since
there are a variety of ways to collect that data. Hard copy records collected
during the calibration of test instruments have been discussed in detail
already. But the collection of data by electronic means, or through the
use of calibration software, process controllers, etc., should also be
considered. Is the system validated and instrumentation qualified prior
to use? If you are using any type of computerized system, validation of
that software is mandatory. How is the data collected and stored? Is it in
its native format or dumped into a spreadsheet for analysis? All of these
need to be considered to allow for review, analysis, and/or compilation
into your forms, and eventual storage.
The use of computerized data collection brings with it not only
increased productivity and savings in time and effort; but also new
problems in how to collect, manage, review and store the data. It
cannot be emphasized enough the criticality of validating your
software, data lines and storage systems when going entirely electronic
with your calibration records and data management.
“Check the results” means make certain the test equipment meets
the tolerances, accuracies, or upper/lower limits specified in your
procedures or instructions.
There are various ways to do this. Calibration forms should have the
range and their tolerances listed for each piece of test equipment being
calibrated. In some instances it is apparent what the tolerances will be
for the items being calibrated. In other cases it is not quite so apparent.
47
a basic quality calibration program
“Act on the difference” means if the test equipment is out of tolerance,
you must inform the user because they may have to re-evaluate
manufactured goods, change a process or procedure, or recall product.
According to the FDA: “When accuracy and precision limits are not met,
there shall be provisions for remedial action to reestablish the limits and to
evaluate whether there was any adverse effect on the device’s quality.”
You should have a written procedure in place that explains in detail:
• What actions are to be taken by the calibration technician?
• What actions to be taken by the department supervisor and/or
manager?
• What actions to be taken by the responsible owner/user of the
OOT test equipment?
You should have an SOP that explains the responsibilities of the
calibration technician:
• Do they have additional form(s) to complete when OOT
conditions are found?
• Do they require a ‘second set of eyes’ when/if an OOT is found?
• Have they been trained and signed off that they know all the
proper procedures when an OOT has been found?
You should have an SOP that explains the responsibilities of the
supervisor/manager:
• Who notifies the customer – the technician, supervisor or
manager?
• Is a data base maintained on all OOT test equipment?
• Is the customer/user required to reply to the OOT notification;
if so is there a time limit, and a paper trail for historical
reference?
After owner/user notification, is the calibration department
responsible for anything else?
• Is the final action by the owner/user sent back for filing or
archiving?
• Usually the department that generates an action item is responsible
for final archiving.
• Are there any databases that need to be updated; or upper
management notification in case of ‘in action’?
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a basic quality calibration program
Do you have a database of all OOT test equipment for various
activities?
• The database can be used for accessing yearly calibration interval
analysis.
• Access to OOT data can assist in determining reliability of test
equipment.
• During an audit/inspection (both internal and external) access to
past OOT data should be easily available.
Here is a hypothetical example: from an historical perspective,
generally 85% of test equipment passes calibration.
• Among the 15% that are found to be OOT some will be due to
Typical calibration
process as shown
in a flow chart
Start
‘As found’
test
Save
‘As found’
results
NO
Adjustment
required?
‘As Left’
test
YES
YES
Adjust
as needed
Within
limits?
NO
Save
‘As Left’
results
End
49
a basic quality calibration program
operator error, bad standards, bad cables/accessories, poorly written
calibration procedures, environmental conditions (vibration, etc.).
• If a higher fail rate is noticed, before changing calibration intervals,
check that the proper specifications are being used.
Developing a world-class calibration program
A quality calibration program might be compared to an iceberg. Only
about 10% can be easily seen by the casual observer. However, the
unseen portion is what keeps the iceberg afloat and stable in the ocean.
The same can be said of a quality calibration program. The “Say
what you do, Do what you say, Record what you did, Check the results,
and Act on the difference” portion, along with traceability should be
apparent to an auditor or inspector. But the different parts that keep
a quality calibration program running efficiently consist of elements
from a continuous process improvement program, scheduling and
calibration management software, an effective training program, a
comprehensive calibration analysis program, correct and properly
used calibration and equipment labels, and a visible safety program.
Without any one of these programs, a quality calibration program
would be impossible to maintain.
Having an effective calibration management program is usually the
difference between being proactive and reactive to performing your
routine calibrations. By knowing what is coming due calibration, you
can schedule your technicians, standards, time and other resources
to the best advantage. This can be compared to the person who is
trying to drain the swamp while fighting off the alligators. It is hard
to keep your overdue calibrations at a minimum when all of your time
is spent reacting to items that keep coming due without your prior
knowledge. Any calibration management program worth the money
should have a few critical areas built into their basic program. Those
include: a master inventory list, reverse traceability, the ability to see
a 30 day schedule of items coming due calibration, and the ability to
see all items that are currently overdue calibration. From a managerial
standpoint, the calibration management program should also be able
to show calibrations and repairs by individual items, groups of items
by location/part number, items that are OOT, and other listings that
help to manage your department. According to most standards and
regulations, any software program used must be validated prior to
implementation. This can be accomplished using the manufacturer’s
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a basic quality calibration program
system, or by incorporating an in-house validation system. Either way,
your validation paperwork needs to be available for inspection during
audits and inspections.
A best practice among experienced calibration practitioners is the
calibration of like items, and using your scheduling software to also
perform calibrations in geographical areas or combining calibrations
in local areas. An example of this would be to calibrate all pressure
gages that were shown to be stored or used in a specific area, or floor of
a building. This would be using your time to the best advantage. Also,
if calibrations were to be performed in a ‘clean room’ environment,
and the calibration technician is required to gown-up prior to entry
every time then go into the clean-room, then scheduling all of the
calibrations in that area could increase production and reduce down
time from multiple entries and exits.
Combining the calibration of like items and mixing and matching
items could reduce the task of mundane and boring calibrations. An
example would be to start all temperature calibrations (set water baths
up for their initial temperature readings), then perform several pipette
or balance calibrations, return to set another temperature in the water
baths (doing a few at a time), return to finish the pipette or balance
calibrations, then complete the water baths at their final setting. By not
having to stand around to wait for the water baths to equilibrate, you are
using your time more efficiently, increasing productivity, and keeping
the calibration technician involved and focused instead of bored.
Another critical yet often times misunderstood program is
calibration interval analysis. How often should each type of test
equipment be calibrated? Should the manufacturer’s recommended
interval be the determining factor? Or should the criticality of how the
test equipment is used in your particular production or manufacturing
line be the deciding vote? Your specific situation should be the driving
factor in deciding calibration interval analysis. Most manufacturers
recommend a 12 month calibration interval, depending on usage,
environment, handling, etc. A particular item used in a controlled
environment should be more reliable that one used in a harsher
situation, say outdoors in severe weather. Also, you must consider if the
test equipment is used to determine final product where specifications
are very tight, or used as an item that is coded as “No Calibration
Required” on a loading dock. Each situation should be considered
carefully so that they can be reviewed in the appropriate light.
Calibration interval analysis software can be purchased commercially
51
a basic quality calibration program
and used to evaluate your test equipment. Also, NCSL International
has RP-1, Establishment & Adjustment of Calibration Intervals. This
Recommended Practice (RP) is intended to provide a guide for the
establishment and adjustment of calibration intervals for equipment
subject to periodic calibration. It provides information needed to
design, implement and manage calibration interval determination,
adjustment and evaluation programs. Both management and technical
information are presented in this RP. Several methods of calibration
interval analysis and adjustment are presented. The advantages and
disadvantages of each method are described and guidelines are given
to assist in selecting the best method for a requiring organization.
A company could also do their own analysis if they support a limited
number of items, or are on a tight budget and are willing to do their
own computations. Here is an example.
• For each type of equipment, collect data over a one year period
on: number of calibrations and number of items OOT
• Take the number of calibrations minus the number of OOTs,
divide result by the number of calibrations, then take the result
times 100 for the pass rate
• Make a risk assessment of each item for your company’s needs; set
a cut off for increasing or decreasing calibration intervals
• Consider increasing a calibration interval if the pass rate ≥ 95%
(by ½ up to double the current calibration interval)
• Consider decreasing a calibration interval if the pass rate ≤ 85%
(by ¾ to ½ of the current calibration interval)
No matter which route you take for calibration interval analysis
– ensure you are on the cutting-edge – not on the ragged-edge by
extending your intervals too fast without solid data; recalls can be
very expensive, in time and money, and to your company’s reputation!
The cost and risk of not calibrating
Are there costs and/or risks associated to not calibrating your test
equipment? This is a double edged sword. On one side we have the
requirement of standards and regulations that govern various companies,
industries and even countries. Not only is calibration a requirement, but
one of the foundations for any quality system in the 21st century. It isn’t
a question of do you have a quality calibration program in place, but
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a basic quality calibration program
does it comply with all the requirements of the appropriate standard or
regulation to which your company must conform?
The other side of the double edged sword is having a calibration
program in place without any type of quality, traceability or
documentation. This would equate to not having any type of
calibration program at all. If a manufacturer produces any type of
product or service where repeatable measurements take place then
their test equipment/instruments need to have repetitive outputs.
Without calibration to a traceable standard (national, international,
or intrinsic), there can be no repeatability. Therefore there can be no
quality in the product, so the company would never be able to stay in
business long enough to impact their market segment.
So is there cost and risk? Absolutely. The cost is huge in terms of lost
production, time, money, and reputation. In the case of companies
that have untraceable calibration in the production of medical devices,
pharmaceutical drugs and products that impact human safety – the
cost could be immeasurable…with the possibility of death among the
results.
The basic belief is this – it is absolutely essential to have a quality
calibration program in place to make a quality product, no matter
the size, shape, or quantity. The question that should be asked is:
“Do you have a quality calibration program that has traceable results
to a national or international standard”? If the answer is yes, then it
is assumed that to have a quality calibration program, you must also
have all the parts needed to support traceable calibration: calibration
procedures, calibration records, traceable documentation, an out-oftolerance program and procedures, document control procedures, a
training program, continuous process improvements, a comprehensive
calibration management software package, calibration interval
analysis, documented training for all your calibration technicians,
and the ability to provide quality customer service in a timely manner.
Then you can say you have a quality calibration program.
But it doesn’t end there. Referring to a double edged sword, what
are the responsibilities of a quality calibration department and also
those of their customer?
A calibration/metrology department should be responsible for:
• Listening to their customers to understand their requirements
and needs
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a basic quality calibration program
• Translating those requirements to the accuracy and
specifications of the test equipment and support services that
meet or exceed their quality expectations
• Delivering test equipment that consistently meets requirements
for reliable performance
• Providing knowledgeable and comprehensive test equipment
support
• Continuously reviewing and improving their services and
processes
Your customers should be responsible for:
• Informing Metrology of their requirements and needs
• Getting the proper training in the correct and safe usage of test
equipment
• Maintaining their test equipment without abusing, contaminating
or damaging it under normal operating conditions
• Using their work order system for requesting service when
equipment is broken, malfunctioning, or in need of calibration
As Lord Kelvin was quoted as saying, “If you cannot measure it, you
cannot improve it.”
1. EAL-G12, Traceability of Measurement. Edition 1, November
1995.
2. EA-4/02, Expression of the Uncertainty of Measurement in
Calibration. December 1999 rev00.
3. Bucher, Jay L. 2007. The Quality Calibration Handbook.
Milwaukee: ASQ Quality Press.
4. NCSL. 1999. Calibration Control Systems for the Biomedical and
Pharmaceutical Industry, RP-6. Boulder, CO.
5. NCSL International. 2006. ANSI/NCSL Z540.3-2006. Boulder,
CO.
54
55
traceable and efficient calibrations
Traceable and efficient calibrations
in the process industry
T
oday’s modern process plants, production processes and quality
systems, put new and tight requirements on the accuracy of
process instruments and on process control.
Quality systems, such as the ISO9000 and ISO14000 series of quality
standards, call for systematic and well-documented calibrations, with
regard to accuracy, repeatability, uncertainty, confidence levels etc.
Does this mean that the electricians and instrumentation people
should be calibration experts? Not really, but this topic should
not be ignored. Fortunately, modern calibration techniques and
calibration systems have made it easier to fulfill the requirements on
instrumentation calibration and maintenance in a productive way.
However, some understanding of the techniques, terminology and
methods involved in calibration must be known and understood in
order to perform according to International Quality Systems.
Calibration can briefly be
described as an activity
where theinstrument
being tested is compared
to a known reference
value, i.e. calibrator.
1. What is calibration and why calibrate
Calibration can brief ly be described as an activity where the
instrument being tested is compared to a known reference value, i.e.
calibrator. The keywords here are ‘known reference’, which means
that the calibrator used should have a valid, traceable calibration
certificate.
To be able to answer the question why calibrate, we must first
determine what measurement is and why measuring is necessary.
57
traceable and efficient calibrations
WHAT IS MEASUREMENT?
In technical standards terms the word measurement has been
defined as:
“A set of experimental operations for the purpose of determining
the value of a quantity.”
What is then the value of quantity? According to the standards
the true value of a quantity is:
“The value which characterizes a quantity perfectly defined
during the conditions which exist at the moment when the value
is observed. Note: the true value of a quantity is an ideal concept
and, in general, it cannot be known.”
Therefore all instruments display false indications!
A set of experimental
operations for the
purpose of determining
the value of a quantity.
HIERARCHY
OF ACCURACY
TRUE VALUE
International
National standard
Authorized
Laboratories
Instr. Departments
House and working standards
Process instrumentation
58
traceable and efficient calibrations
2. Why measure?
The purpose of a process plant is to convert raw material, energy,
manpower and capital into products in the best possible way. This
conversion always involves optimizing, which must be done better
than the competitors. In practice, optimization is done by means of
process automation. Anyhow, regardless of how advanced the process
automation system is, the control cannot be better than the quality of
measurements from the process.
3. Why calibrate
The primary reason for calibrating is based on the fact that even the
best measuring instruments lack in absolute stability, in other words,
The primary reason for
calibrating is based on
the fact that even the best
measuring instruments
lack in absolute stability, in
other words, they drift and
lose their ability to give
accurate measurements.
EVERYTHING IS BASED
ON MEASUREMENTS
PROCESS CONTROL SYSTEM
MEASUREMENTS
CONTROLS
INSTRUMENTATION
MEASUREMENTS
Production
Factors
ADJUSTMENTS
PROCESS
Products
59
traceable and efficient calibrations
they drift and lose their ability to give accurate measurements. This
drift makes recalibration necessary.
Environment conditions, elapsed time and type of application can
all affect the stability of an instrument. Even instruments of the same
manufacturer, type and range can show varying performance. One
unit can be found to have good stability, while another performs
differently.
Other good reasons for calibration are:
Environment conditions,
elapsed time and type
of application can all
affect the stability of an
instrument.
• To maintain the credibility of measurements
• To maintain the quality of process instruments
at a good-as-new level
• Safety and environmental regulations
• ISO9000, other quality systems and regulations
The ISO9000 and ISO14000 can assist in guiding regular, systematic
calibrations, which produces uniform quality and minimizes the
negative impacts on the environment.
QUALITY MAINTENANCE
QUALITY
QP
C1 C2
C1–C7 CALIBRATIONS
C3
C4
“GOOD AS NEW”
C5 C6 C7
QM
LOWER
TOLERANCE
Q1
Q2
Q3
QZM
PURCHASE
T1
T2
QP – PURCHASED QUALITY
QZM – ZERO MAINTAINED QUALITY
QM – MAINTAINED QUALITY
60
T3
TIME
traceable and efficient calibrations
4. Traceability
Calibrations must be traceable. Traceability is a declaration stating
to which national standard a certain instrument has been compared.
5. Regulatory requirements for calibration
5.1 ISO9001: 2008
The organization determines the monitoring and measurements to
be performed, as well as the measuring devices needed to provide
evidence of a product’s conformity to determined standards.
The organization establishes the processes for ensuring that
measurements and monitoring are carried out and are carried out
in a manner consistent with the monitoring and measurement
requirements.
Where necessary, to ensure valid results, measuring equipment
is calibrated or verified with measurement standards traceable to
national or international standards at specified intervals. If no
such standards exist, the basis used for calibration or verification
is recorded; adjusted or re-adjusted as necessary; identified for the
determining of the calibration status; safeguarded against adjustments
that would invalidate the measurement result; protected from damage
and deterioration during handling, maintenance and storage.
In addition, the organization assesses and records the validity of
the previous measuring results when the equipment is found not to
conform to requirements. The organization then takes appropriate
action on the equipment and any product affected. Records of the
calibration and verification results are then maintained.
When used in the monitoring and measurement of specified
requirements, the ability of computer software to satisfy the intended
application is confirmed. This is done prior to initial use and
reconfirmed as necessary.
SI-UNITS
International
standards
National
standards
Reference
standards
Working
standards
Process
standards
Note: See ISO 10012 for further information.
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traceable and efficient calibrations
5.2 PHARMACEUTICAL (FDA, U.S. Food and Drug Administration)
Any pharmaceutical company that sells their products in the USA
must comply with FDA regulations, regardless of where the products
are manufactured.
Software systems
need features such as
Electronic Signature, Audit
Trail, User Management,
and Security System
to be able to comply
with these regulations.
• Calibration records must be maintained.
• Calibrations must be done in accordance with written, approved
procedures.
• There should be a record of the history of each instrument.
• All instrumentation should have a unique ID; all product, process
and safety instruments should be physically tagged.
• A calibration period and error limits should be defined for each
instrument.
• Calibration standards should be traceable to national and
international standards.
• Calibration standards must be more accurate than the required
accuracy of the equipment being calibrated.
• All instruments used must be fit for purpose.
• There must be documented evidence that personnel involved in
the calibration process have been trained and are competent.
• Documented change management system must be in place.
• All electronic systems must comply with FDA’s 21 CFR Part 11.
• All of the above should be implemented in conjunction with
following regulations:
– 21 CFR Part 211 – “Current Good Manufacturing Practice
for Finished Pharmaceuticals”
– 21 CFR Part 11 – “Electronic Records; Electronic Signatures”
Software systems need features such as Electronic Signature, Audit
Trail, User Management, and Security System to be able to comply
with these regulations.
In such a system, the Electronic Signature is considered equivalent to
a hand-written signature. Users must understand their responsibilities
once they give an electronic signature. An Audit Trail is required
to support change management. Audit Trails should record all
modifications, which add, edit, or delete data from an electronic
record.
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traceable and efficient calibrations
5.3 PHARMACEUTICAL (EU GMPs)
Any pharmaceutical company that sells their products in the European
Union must comply with EU GMPs, including Annex 11, regardless of
where the products are manufactured.
The requirements for EU GMPs are similar to those of the US FDA,
as described in Section 5.2.
6. DEFINITIONS OF METROLOGICAL TERMS
Some metrological terms in association with the concept of calibration
are described in this section.
Quite a few of the following terms are also used on specification
sheets for calibrators. Please note that the definitions listed here are
simplified.
Calibration
An unknown measured signal is compared to a known reference
signal.
Validation of measure­
ment and test methods
(procedures) is generally
necessary to prove that
the methods are suitable
for the intended use.
Validation
Validation of measurement and test methods (procedures) is generally
necessary to prove that the methods are suitable for the intended use.
Non-linearity
Non-linearity is the maximum deviation of a transducer’s output from
a defined straight line. Non-linearity is specified by the Terminal
Based method or the Best Fit Straight Line method.
Resolution
Resolution is the smallest interval that can be read between two
readings.
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traceable and efficient calibrations
Sensitivity
Sensitivity is the smallest variation in input, which can be detected as
an output. Good resolution is required in order to detect sensitivity.
Hysteresis
The deviation in output at any point within the instrument’s sensing
range, when first approaching this point with increasing values, and
then with decreasing values.
Stability is expressed as
the change in percentage
in the calibrated output
of an instrument over a
specified period, usually
90 days to 12 months,
under normal operating
conditions.
Repeatability
Repeatability is the capability of an instrument to give the same
output among repeated inputs of the same value over a period of time.
Repeatability is often expressed in the form of standard deviation.
Temperature coefficient
The change in a calibrator’s accuracy caused by changes in ambient
temperature (deviation from reference conditions). The temperature
coefficient is usually expressed as % F.S. / °C or % of RDG/ °C.
Stability
Often referred to as drift, stability is expressed as the change in
percentage in the calibrated output of an instrument over a specified
period, usually 90 days to 12 months, under normal operating
conditions. Drift is usually given as a typical value.
Accuracy
Generally accuracy figures state the closeness of a measured value
to a known reference value. The accuracy of the reference value is
generally not included in the figures. It must also be checked if errors
like non-linearity, hysteresis, temperature effects etc. are included in
the accuracy figures provided.
Accuracy is usually expressed % F.S. or % of RDG + adder. The
difference between these two expressions is great. The only way to
compare accuracy presented in different ways is to calculate the total
error at certain points.
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traceable and efficient calibrations
Uncertainty
Uncertainty is an estimate of the limits, at a given cover factor (or
confidence level), which contain the true value.
Uncertainty is evaluated according to either a “Type A” or a “Type
B” method. Type A involves the statistical analysis of a series of
measurements. In this case, uncertainty is calculated using Type A
uncertainties, i.e. the effects of these components include measurement
errors, which can vary in magnitude and in sign, in an unpredictable
manner. The other group of components, Type B, could be said to be of
a systematic nature. Systematic errors or effects remain constant during
the measurement. Examples of systematic effects include errors in
reference value, set-up of the measuring, ambient conditions, etc. Type
B uncertainty is used when the uncertainty of a single measurement
is expressed.
It should be noted that, in general, errors due to observer fallibility
cannot be accommodated within the calculation of uncertainty.
Examples of such errors include: errors in recording data, errors in
calculation, or the use of inappropriate technology.
It should be noted that, in
general, errors due to
observer fallibility cannot
be accommodated within
the calculation
of uncertainty.
Type A uncertainty
The type A method of calculation can be applied when several
independent measurements have been made under the same
conditions. If there is sufficient resolution in the measurement, there
will be an observable difference in the values measured.
The standard deviation, often called the “root-mean-square
repeatability error”, for a series of measurements under the same
conditions, is used for calculation. Standard deviation is used as a
measure of the dispersion of values.
Type B uncertainty
Type B evaluation of uncertainty involves the use of other means
to calculate uncertainty, rather than applying statistical analysis of a
series of measurements.
It involves the evaluation of uncertainty using scientific judgement
based on all available information concerning the possible variables.
Values belonging to this category may be derived from:
65
traceable and efficient calibrations
• Experience with or general knowledge of the behavior
and properties of relevant materials and instruments
• Ambient temperature
• Humidity
• Local gravity
• Atmospheric pressure
• Uncertainty of the calibration standard
• Calibration procedures
• Method used to register calibration results
• Method to process calibration results
For uncertainty
specifications, there
must be a clear state­ment of cover probability
or confidence level.
The proper use of the available information calls for insight based
on experience and general knowledge. It is a skill that can be learnt
with practice. A well-based Type B evaluation of uncertainty can
be as reliable as a Type A evaluation of uncertainty, especially in
a measurement situation where a Type A evaluation is based only
on a comparatively small number of statistically independent
measurements.
Expanded uncertainty
The EA has decided that calibration laboratories accredited
by members of the EA shall state an expanded uncertainty of
measurement obtained by multiplying the uncertainty by a coverage
factor k. In cases where normal (Gaussian) distribution can be
assumed, the standard coverage factor, k=2, should be used. The
expanded uncertainty corresponds to a coverage probability (or
confidence level) of approximately 95%.
For uncertainty specifications, there must be a clear statement of
cover probability or confidence level. Usually one of the following
confidence levels are used:
1 s = 68%
2 s = 95%
3 s = 99%
7. CALIBRATION MANAGEMENT
Many companies do not pay enough attention to calibration
management although it is a requirement e.g. in ISO9001: 2008.
The maintenance management system may alert when calibration is
66
traceable and efficient calibrations
needed and then opens up a work order. Once the job has been done,
the work order will close and the maintenance system will be satisfied.
Unfortunately, what happens between opening and closing of the
work order is not documented very often. If something is documented,
it is usually in the form of a hand-written sheet that is then archived.
If the calibration results need to be examined at a later time, finding
the sheets requires a lot of effort.
Choosing professional tools for maintaining calibration records
and doing the calibrations can save a lot of time, effort and money.
An efficient calibration management system consists of calibration
management software and documenting calibrators.
Modern calibration management software can be a tool that
automates and simplifies calibration work at all levels. It automatically
creates a list of instruments waiting to be calibrated in the near future.
If the software is able to interface with other systems the scheduling
of calibrations can be done in the maintenance system from which
the work orders can be automatically loaded into the calibration
management software.
When the technician is about to calibrate an instrument, (s)he simply
downloads the instrument details from the calibration management
software into the memory of a documenting calibrator; no printed
notes, etc. are needed. The “As Found” and “As Left” are saved in the
calibrator’s memory, and there is no need to write down anything
with pen.
The instrument’s measurement ranges and error limits are defined in
the software and also downloaded to the calibrator. Thus the calibrator
is able to detect if the calibration was passed or failed immediately after
the last calibration point was recorded. There is no need to make tricky
calculations manually in the field.
All this saves an extensive amount of time and prevents the user
from making mistakes. The increase in work productivity allows for
more calibrations to be carried out within the same period of time
as before. Depending on what process variable is calibrated and how
many calibration points are recorded, using automated tools can be 5
to 10 times faster compared to manual recording.
While the calibration results are uploaded onto the database, the
software automatically detects the calibrator that was used, and the
traceability chain is documented without requiring any further actions
from the user.
Calibration records, including the full calibration history of an
The instrument’s
measurement ranges
and error limits are
defined in the software
and also downloaded
to the calibrator.
67
traceable and efficient calibrations
Implementing a modern
calibration management
system benefits
everybody who has
anything to do with
instrumentation.
68
instrument, are kept in the database; therefore accessing previous
results is also possible in just a few seconds. When an instrument has
been calibrated several times, software displays the “History Trend”,
which assists in determining whether or not the calibration period
should be changed.
One of today’s trends is to move towards to a paperless office. If the
calibration management software includes the right tools, it is possible
to manage calibration records on computer without producing any
papers. If paper copies of certificates are preferred, printing them must,
of course, be possible. When all calibration related data is located in
a single database the software is obviously able to create calibration
related reports and documents.
Today’s documenting calibrators are capable of calibrating many
process signals. It is not very uncommon to have a calibrator that
calibrates pressure, temperature and electrical signals including
frequency and pulses. In addition to the conventional mA output of
a transmitter, modern calibrators can also read HART, Foundation
Fieldbus or Profibus output of the transmitters, and they can be even
used for configuring these “smart” transmitters.
Implementing a modern calibration management system benefits
everybody who has anything to do with instrumentation. For instance
the maintenance manager can use it as a calibration planning and
decision-making tool for tracking and managing all calibration related
activities.
When an auditor comes for a visit, QA will find a calibration
management system useful. The requested calibration records can
be viewed on screen with a couple mouse clicks. If a calibrator drifts
out of its specifications, it is possible to use a “reverse traceability
report” to get a list of instruments that have been calibrated with that
calibrator.
Good calibration tools help technicians work more efficiently and
accurately. If the system manufacturer has paid attention usability,
the system is easy to learn and use. When many tasks are automated,
the users can concentrate on their primary job.
Transferring to a new calibration system may sound like a huge task
and it can be a huge task. There are probably thousands of instruments
that need to be entered into the database and all the details must be
checked and verified before the system is up and running. Although
there is a lot of data involved, it does not mean the job is an enormous
one.
traceable and efficient calibrations
Nowadays most companies have instrumentation data in some type
of electronic format: as Excel spreadsheets, Maintenance databases,
etc. The vendor of the calibration system is most likely able to import
most of the existing data to the calibration database saving months
of work.
CONCLUSION
A good, automated calibration system reduces workload
because it carries out tasks faster, more accurately and with
better results than what could be reached with a manual system.
It assists in documenting, scheduling, planning, analyzing and
finally optimizing the calibration work.
A good, automated
calibration system
reduces workload.
References
[1] ISO9001: 2008 “Quality Management Systems.
Requirements”
[2] 21 CFR Part 11: “Electronic Records;
Electronic Signatures”
[3] 21 CFR Part 211: “Current Good Manufacturing Practice
for Finished Pharmaceuticals”
69
Calibration
Management and
Maintenance
why calibrate
Why Calibrate?
What is the risk of not calibrating?
C
alibration can be briefly described as an activity where the
instrument being tested is compared to a known reference
value. At the simplest level, calibration is a comparison between
measurements – one of known magnitude or correctness made or set
with one device, and another measurement made in as similar a way as
possible with a second device. The device with the known or assigned
correctness is called the standard. The second device is the unit under
test or test instrument.
Calibration is often required with a new instrument or when a
specified time period or a specified number of operating hours
has elapsed. In addition, calibration is usually carried out when an
instrument has been subjected to an unexpected shock or vibration
that may have put it out of its specified limits.
Although drift cannot be
completely eliminated, it
can be discovered and
rectified via calibration.
Calibration in industrial applications
When a sensor or instrument experiences temperature variations or
physical stress over time, its performance will invariably begin to
decline, which is known as ‘drift’. This means that measurement data
from the sensor becomes unreliable and could even affect the quality
of a company’s production.
Although drift cannot be completely eliminated, it can be discovered
and rectified via calibration. The purpose of calibration is to determine
how accurate an instrument or sensor is. Although most instruments
provide high accuracy these days, regulatory bodies often need to
know just how inaccurate a particular instrument is and whether it
drifts in and out of specified tolerance over time.
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why calibrate
The costs and risks of not calibrating
Even the highest quality
instruments will drift
over time and lose their
ability to provide accurate
measurements.
Unfortunately, calibration has costs associated with it and in uncertain
economic times, this activity can often become neglected or the
interval between calibration checks on instruments can be extended in
order to cut costs or simply through a lack of resources or manpower.
However, neglecting calibration can lead to unscheduled production
or machine downtime, product and process quality issues or even
product recalls and rework.
Furthermore, if the instrument is critical to a process or is located
in a hazardous area, allowing that sensor to drift over time could
potentially result in a risk to employee safety. Similarly, an end product
manufactured by a plant with poorly calibrated instruments could
present a risk to both consumers and customers. In certain situations,
this may even lead to a company losing its license to operate due to
company not meeting its regulatory requirements. This is particularly
true for the food and beverage sector and for pharmaceutical
manufacturers.
Weighing instruments also need to be calibrated regularly.
Determining the correct mass of a product or material is particularly
important for companies that supply steel, paper and pulp, power,
aviation companies, harbors and retail outlets, who invoice customers
based on the mass of what they supply (fiscal metering). These
companies need to prove not only that the mass is accurate but also
that the equipment producing the readings was correctly calibrated.
Invoicing in these industries is often based on process measurements.
There is therefore a growing need to have the metrological quality of
these weighing instruments confirmed by calibration.
Product manufacturing also depends on accurate masses and so
laboratories and production departments in the food and beverage,
oil and gas, energy, chemical and pharmaceutical industries, also need
to calibrate their weighing instruments.
Why is calibration important?
Calibration ensures that instrument drift is minimized. Even the
highest quality instruments will drift over time and lose their ability
to provide accurate measurements. It is therefore critical that all
instruments are calibrated at appropriate intervals.
The stability of an instrument very much depends on its application
and the environment it operates in. Fluctuating temperatures, harsh
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why calibrate
manufacturing conditions (dust and dirt) and elapsed time are all
contributing factors here. Even instruments manufactured by the same
supplier can vary in their performance over time.
Calibration also ensures that product or batch quality remains high
and consistent over time. Quality systems such as ISO 9001, ISO 9002
and ISO 14001 require systematic, well-documented calibrations with
respect to accuracy, repeatability, uncertainty and confidence levels.
This affects all process manufacturers.
Armando Rivero Rubalcaba is head of Instrumentation at beer
producer Heineken (Spain). He comments: “For Heineken, the quality
of the beer is a number one priority. All the plants in Spain have
received ISO 9001 and ISO 14001 certifications, in addition to the BRC
certificate of food safety. We must therefore ensure that all processes
correspond to the planned characteristics. The role of calibration is very
important to ensure the quality and safety of the processes.”
Pharmaceutical manufacturers must follow current Good
Manufacturing Practices, GMP, requires that calibration records are
maintained and calibrations have to be carried out in accordance
with written, approved procedures. Typically, each instrument has a
master history record and a unique ID. All product, process and safety
instruments should also be physically tagged.
Furthermore, a calibration interval and error limits should be
defined for each instrument and standards should be traceable to
national and international standards. Standards must also be more
accurate than the required accuracy of the equipment being calibrated.
On the people side, there must be documented evidence that
employees involved in the calibration process have been properly
trained and competent. The company must also have a documented
change management system in place, with all electronic systems
complying with FDA regulations 21 CFR Part 11.
In the power generation, energy and utilities industries, instrument
calibration can help to optimize a company’s production process or to
increase the plant’s production capacity. For example, at the Almaraz
Nuclear Power Plant in Spain, by improving the measurement of
reactor power parameters from 2% to 0.4%, enabled the reactor power
in each unit to be increased by 1.6%, which has a significant effect on
annual production capacity.
Safety is another important reason to calibrate instruments.
Production environments are potentially high risk areas for employees
and can involve high temperatures and high pressures. Incorrect
measurements in a hazardous area could lead to serious consequences,
The role of calibration is
very important to ensure
the quality and safety of
the processes.
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why calibrate
Calibration is of great
importance, especially
from the viewpoint of
production safety and
quality of the final product.
76
particularly in the oil and gas, petrochemicals and chemicals sectors.
Similarly, manufacturers of food and beverage or pharmaceutical
products could put their customers’ lives at risk by neglecting to
calibrate their process instruments.
Heikki Karhe is a measurement technician at the tyre manufacturer
Nokian Tyres. As he puts it: “Calibration is of great importance,
especially from the viewpoint of production safety and quality of
the final product. Preparation of the right rubber mixture is precision
work and a sample is taken from each rubber mixture to ensure quality.
Measuring instruments that yield wrong values could easily ruin the
final product. The factory is also full of pressure instruments and so it
is also important for the safety of the workers that those instruments
show the right values.”
Neglecting to calibrate process instruments can also affect a
company’s bottom line profits. This is particularly true if sales
invoicing is based on accurate process measurements, for example,
weighing scales or gas conversion devices. Indeed, according to recent
research by Nielsen Research/ ATS Studies, poor quality calibration
is on average costing manufacturers more than 1.7 million US dollars
every year. When only large companies with revenues of more than 1
billion US dollars are considered, this figure rises dramatically to more
than 4 million US dollars per year.
Proper invoicing is therefore critical to energy and utilities
companies. As Jacek Midera, measurement specialist at Mazovian Gas
Company states: “Most importantly, accurate measurements ensure
proper billing. The impact of even a small measurement error can
be tremendous in terms of lost revenue. Customers want to pay for
the exact amount of gas they’ve received. Therefore, gas conversion
devices must be extremely accurate in measuring delivered gas. This
means that requirements for the calibrators are especially high.”
Today, controlling emissions is another critical factor for many
process manufacturers. Calibrating instruments can help to make
combustion more efficient in industrial ovens and furnaces. The
latest Government regulations relating to carbon emissions may also
require that companies calibrate specific instruments on a regular
basis, including sensors used for measuring CO2 and NOX emissions.
As Ed de Jong, Instrument Maintenance Engineer at Shell
(Netherlands) explains: “Until recently, calibration was mainly driven
by economic motives: even the smallest of errors in delivery quantities
are unacceptable in Shell’s operation due to the vast sums of money
why calibrate
involved for both customers and governments [fiscal metering].
Nowadays, calibration has an important role especially for the license
to operate. Government regulations demand that specific instruments
must be calibrated, for example, instruments related to CO2 and NOX
emissions.”
Common misconceptions
There are some common misconceptions when it comes to instrument
calibration. For example, some manufacturers claim that they do not
need to calibrate their fieldbus instruments because they are digital
and so are always accurate and correct. This is simply not true. The
main difference between fieldbus and conventional transmitters
is that the output signal is a fully digital fieldbus signal. Changing
the output signal does not change the need for periodic calibration.
Although fieldbus transmitters have been improved in terms of their
measurement accuracy when compared to analogue transmitters, this
does not eliminate the need for calibration.
Another common misunderstanding is that new instruments do
not require calibration. Again, this is not true. Just because a sensor is
newly installed does not mean that it will perform within the required
specifications. By calibrating an instrument before installation,
a company is able to enter all the necessary instrument data to its
calibration database or calibration management software, as well as
begin to monitor the stability or drift of the instrument over time.
The most effective
method of determining
when an instrument
requires calibrating is to
use some sort of history
trend analysis.
When to calibrate
Due to drift, all instruments require calibrating at set intervals. How
often they are calibrated depends on a number of factors. First, the
manufacturer of the instrument will provide a recommended calibration
interval. This interval may be decreased if the instrument is being used
in a critical process or application. Quality standards may also dictate
how often a pressure or temperature sensor needs calibrating.
The most effective method of determining when an instrument
requires calibrating is to use some sort of history trend analysis. The
optimal calibration interval for different instruments can only be
determined with software-based history trend analysis. In this way,
highly stable sensors are not calibrated as often as those sensors that
are more susceptible to drift.
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why use software for calibration management
Why use software for
calibration management?
E
very manufacturing plant has some sort of system in place for
managing instrument calibration operations and data. Plant
instrumentation devices such as temperature sensors, pressure
transducers and weighing instruments – require regular calibration
to ensure they are performing and measuring to specified tolerances.
However, different companies from a diverse range of industry
sectors use very different methods of managing these calibrations.
These methods differ greatly in terms of cost, quality, efficiency, and
accuracy of data and their level of automation.
Calibration software is one such tool that can be used to support and
guide calibration management activities, with documentation being
a critical part of this.
But in order to understand how software can help process plants
better manage their instrument calibrations, it is important to consider
the typical calibration management tasks that companies have to
undertake. There are five main areas here, comprising of planning
and decision-making; organisation; execution; documentation; and
analysis.
Careful planning and decision-making is important. All plant
instruments and measurement devices need to be listed, then classified
into ‘critical’ and ‘non-critical’ devices. Once this has been agreed,
the calibration range and required tolerances need to be identified.
Decisions then need to be made regarding the calibration interval for
each instrument. The creation and approval of standard operating
procedures (SOPs) for each device is then required, followed by the
selection of suitable calibration methods and tools for execution of
these methods. Finally, the company must identify current calibration
status for every instrument across the plant.
Calibration software
is one such tool that
can be used to support
and guide calibration
management activities,
with documentation being
a critical part of this.
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why use software for calibration management
All plant instruments and
measurement devices
need to be listed, then
classified into ‘critical’
and ‘non-critical’ devices.
The next stage, organisation, involves training the company’s
calibration staff – typically maintenance technicians, service
engineers, process and quality engineers and managers – in using the
chosen tools and how to follow the approved SOPs. Resources then
have to be organised and assigned to actually carry out the scheduled
calibration tasks.
The execution stage involves supervising the assigned calibration
tasks. Staff carrying out these activities must follow the appropriate
instructions before calibrating the device, including any associated
safety procedures. The calibration is then executed according to the plan,
although further instructions may need to be followed after calibration.
The documentation and storage of calibration results typically
involves signing and approving all calibration records that are generated.
The next calibration tasks then have to be scheduled, calibration labels
need to be created and pasted, then created documents copied and
archived.
Based on the calibration results, companies then have to analyse the
data to see if any corrective action needs to be taken. The effectiveness
of calibration needs to be reviewed and calibration intervals checked.
These intervals may need to be adjusted based on archived calibration
history. If, for example, a sensor drifts out of its specification range,
the consequences could be disastrous for the plant, resulting in costly
production downtime, a safety problem or leading to batches of inferior
quality goods being produced, which may then have to be scrapped.
Documentation
Documentation is a very important part of a calibration management
process. ISO 9001:2008 and the FDA both state that calibration
records must be maintained and that calibration must be carried out
according to written, approved procedures.
This means an instrument engineer can spend as much as 50 per
cent of his or her time on documentation and paperwork – time that
could be better spent on other value-added activities. This paperwork
typically involves preparing calibration instructions to help field
engineers; making notes of calibration results in the field; and
documenting and archiving calibration data.
Imagine how long and difficult a task this is if the plant has
thousands of instruments that require calibrating on at least a sixmonthly basis? The amount of manual documentation increases
almost exponentially!
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why use software for calibration management
When it comes to the volume of documentation required, different
industry sectors have different requirements and regulations. In the
Power & Energy sector, for example, just under a third of companies
(with 500+ employees) typically have more than 5,000 instruments
that require calibrating. 42 per cent of companies perform more than
2,000 calibrations each year.
In the highly regulated pharmaceuticals sector, a massive 75 per cent
of companies carry out more than 2,000 calibrations per year. Oil,
Gas & Petrochemicals is similarly high, with 55 per cent of companies
performing more than 2,000 calibrations each year. The percentage
is still quite high in the food & beverage sector, where 21 per cent of
firms said they calibrated their instruments more than 2,000 times
every year. This equates to a huge amount of paperwork for any process
plant.
The figures outlined appear to suggest that companies really
do require some sort of software tool to help them manage their
instrument calibration processes and all associated documentation.
However, the picture in reality can be very different.
Only a quarter of companies use calibration software
In Beamex’s own Calibration Study carried out recently, a mere 25
per cent of companies with 500+ employees (across the industry
sectors mentioned above) said that they did use specialist calibration
management software. Many other companies said that they relied
on generic spreadsheets and/or databases for this, whilst others used
a calibration module within an existing Computerised Maintenance
Management System (CMMS). A significant proportion (almost 20 per
cent) of those surveyed said they used a manual, paper-based system.
Any type of paper-based calibration system will be prone to human
error. Noting down calibration results by hand in the field and then
transferring these results into a spreadsheet back at the office may
seem archaic, but many firms still do this. Furthermore, analysis of
paper-based systems and spreadsheets can be almost impossible, let
alone time consuming.
In a recent survey conducted by Control Magazine, 40 per cent of
companies surveyed said that they calculated calibration intervals by
using historical trend analysis – which is encouraging. However, many
of these firms said they were doing it without any sort of calibration
software to assist them. The other 60 per cent of companies determined
This means an instrument
engineer can spend
as much as 50 per
cent of his or her time
on documentation and
paperwork – time that
could be better spent
on other value-added
activities.
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why use software for calibration management
Using software for
calibration management
enables faster, easier and
more accurate analysis
of calibration records
and identifying historical
trends.
instrument calibration intervals based on either the manufacturer’s own
recommendation, or they used a uniform interval across the plant for
all instruments. Neither method is ideal in practice. Companies could
save so much time and reduce costs by using calibration management
software to analyse historical trends and calibration results.
Using software for calibration management enables faster, easier and
more accurate analysis of calibration records and identifying historical
trends. Plants can therefore reduce costs and optimise calibration
intervals by reducing calibration frequency when this is possible, or
by increasing the frequency where necessary.
For example, for improved safety, a process plant may find it
necessary to increase the frequency of some sensors that are located in
a hazardous, potentially explosive area of the manufacturing plant.
Just as important, by analysing the calibration history of a flow
meter that is located in a ‘non-critical’ area of the plant, the company
may be able to decrease the frequency of calibration, saving time and
resources. Rather than rely on the manufacturer’s recommendation for
calibration intervals, the plant may be able to extend these intervals by
looking closely at historical trends provided by calibration management
software. Instrument ‘drift’ can be monitored closely over a period of
time and then decisions taken confidently with respect to amending
the calibration interval.
Regardless of industry sector, there seems to be some general
challenges that companies face when it comes to calibration
management.
The number of instruments and the total number of periodic
calibrations that these devices require can be several thousand per year.
How to plan and keep track of each instrument’s calibration procedures
means that planning and scheduling is important. Furthermore, every
instrument calibration has to be documented and these documents
need to be easily accessible for audit purposes.
Paper-based systems
These systems typically involve hand-written documents. Typically,
this might include engineers using pens and paper to record calibration
results while out in the field. On returning to the office, these notes
are then tidied up or transferred to another paper document, after
which they are archived as paper documents.
While using a manual, paper-based system requires little or no
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why use software for calibration management
investment, it is very labour-intensive and means that historical trend
analysis becomes very difficult to carry out. In addition, the calibration
data is not easily accessible. The system is time consuming, soaks up a
lot of resources and typing errors are commonplace. Dual effort and
re-keying of calibration data are also significant costs here.
In-house legacy systems (spreadsheets, databases, etc.)
Although certainly a step in the right direction, using an in-house
legacy system to manage calibrations has its drawbacks. In these
systems, calibration data is typically entered manually into a
spreadsheet or database. The data is stored in electronic format, but
the recording of calibration information is still time-consuming and
typing errors are common. Also, the calibration process itself cannot
be automated. For example, automatic alarms cannot be set up on
instruments that are due for calibration.
Calibration module of a CMMS
Many plants have already invested in a Computerised Maintenance
Management (CMM) system and so continue to use this for calibration
management. Plant hierarchy and works orders can be stored in the
CMM system, but the calibration cannot be automated because the
system is not able to communicate with ‘smart’ calibrators.
Furthermore, CMM systems are not designed to manage calibrations
and so often only provide the minimum calibration functionality, such
as the scheduling of tasks and entry of calibration results. Although
instrument data can be stored and managed efficiently in the plant’s
database, the level of automation is still low. In addition, the CMM
system may not meet the regulatory requirements (e.g. FDA) for
managing calibration records.
Regardless of industry
sector, there seems to be
some general challenges
that companies face
when it comes to
calibration management.
Calibration software
With specialist calibration management software, users are provided
with an easy-to-use Windows Explorer-like interface. The software
manages and stores all instrument and calibration data. This
includes the planning and scheduling of calibration work; analysis
and optimisation of calibration frequency; production of reports,
certificates and labels; communication with smart calibrators; and
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why use software for calibration management
easy integration with CMM systems such as SAP and Maximo. The
result is a streamlined, automated calibration process, which improves
quality, plant productivity and efficiency.
Benefits of using calibration software
Using software for
calibration management
enables faster, easier and
more accurate analysis
of calibration records
and identifying historical
trends.
84
With software-based calibration management, planning and decisionmaking are improved. Procedures and calibration strategies can be
planned and all calibration assets managed by the software. Position,
device and calibrator databases are maintained, while automatic alerts
for scheduled calibrations can be set up.
Organisation also improves. The system no longer requires pens and
paper. Calibration instructions are created using the software to guide
engineers through the calibration process. These instructions can also
be downloaded to a technician’s handheld documenting calibrator
while they are in the field.
Execution is more efficient and errors are eliminated. Using
software-based calibration management systems in conjunction with
documenting calibrators means that calibration results can be stored
in the calibrator’s memory, then automatically uploaded back to the
calibration software. There is no re-keying of calibration results from
a notebook to a database or spreadsheet. Human error is minimised
and engineers are freed up to perform more strategic analysis or other
important activities.
Documentation is also improved. The software generates reports
automatically and all calibration data is stored in one database rather
than multiple disparate systems. Calibration certificates, reports and
labels can all be printed out on paper or sent in electronic format.
Analysis becomes easier too, enabling engineers to optimise calibration
intervals using the software’s History Trend function.
Also, when a plant is being audited, calibration software can
facilitate both the preparation and the audit itself. Locating records
and verifying that the system works is effortless when compared to
traditional calibration record keeping.
Regulatory organisations and standards such as FDA and ISO
place demanding requirements on the recording of calibration data.
Calibration software has many functions that help in meeting these
requirements, such as Change Management, Audit Trail and Electronic
Signature functions. The Change Management feature in Beamex’s
CMX software, for example, complies with FDA requirements.
Business benefits
For the business, implementing software-based calibration management
means overall costs will be reduced. These savings come from the
now-paperless calibration process, with no manual documentation
procedures. Engineers can analyse calibration results to see whether
the calibration intervals on plant instruments can be altered. For
example, those instruments that perform better than expected may
well justify a reduction in their calibration frequency.
Plant efficiencies should also improve, as the entire calibration process
is now streamlined and automated. Manual procedures are replaced
with automated, validated processes, which is particularly beneficial if
the company is replacing a lot of labour-intensive calibration activities.
Costly production downtime will also be reduced.
Even if a plant has already implemented a CMM system, calibration
management software can be easily integrated to this system. If the
plant instruments are already defined on a database, the calibration
management software can utilise the records available in the CMM
system database.
The integration will save time, reduce costs and increase productivity
by preventing unnecessary double effort and re-keying of works orders
in multiple systems. Integration also enables the plant to automate its
calibration management with smart calibrators, which simply is not
possible with a standalone CMM system.
Benefits for all process plants
Beamex’s suite of calibration management software can benefit all
sizes of process plant. For relatively small plants, where calibration
data is needed for only one location, only a few instruments require
calibrating and where regulatory compliance is minimal, Beamex
CMX Light is the most appropriate software.
For medium-to-large sized companies that have multiple users who
have to deal with a large amount of instruments and calibration work, as
well as strict regulatory compliance, Beamex CMX Professional is ideal.
Beamex’s high-end solution, CMX Enterprise, is suitable for process
manufacturers with multiple global sites, multilingual users and a very
large amount of instruments that require calibration. Here, a central
calibration management database is often implemented that is used
by multiple plants across the world.
CHECKLIST
Choosing the right
calibration software
• Is it easy to use?
• What are the specific
requirements in terms
of functionality?
• Are there any IT
requirements or
restrictions for choosing
the software?
• Does the calibration
software need to be
integrated with the plant’s
existing systems?
• Is communication with
smart calibrators a
requirement?
• Does the supplier offer
training, implementation,
support and upgrades?
• Does the calibration
software need to be
scalable?
• Can data be imported
to the software from the
plant’s current systems?
• Does the software offer
regulatory compliance?
• Supplier’s references and
experience as a software
developer?
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why use software for calibration management
SUMMARY
Calibration software
improves calibration
management tasks
in all these areas
• Planning &
decision-making
• Organisation
• Execution
• Documentation
• Analysis
The business benefits
of using software for
calibration management
• Cost reduction
• Quality improvements
• Increase in efficiency
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Beamex users
Beamex conducted recently a survey of its customers, across all
industry sectors. The results showed that 82% of CMX Calibration
software customers said that using Beamex products had resulted in
cost savings in some part of their operations.
94% of CMX users stated that using Beamex products had improved
the efficiency of their calibration processes, whilst 92% said that using
CMX had improved the quality of their calibration system.
Summary
Every type of process plant, regardless of industry sector, can benefit
from implementing specialist calibration management software.
Compared to traditional, paper-based systems, in-house built legacy
calibration systems or calibration modules with CMM systems, using
dedicated calibration management software results in improved
quality, increased productivity and reduced costs of the entire
calibration process.
Despite these benefits, only one quarter of companies who need
to manage instrument calibrations actually use software designed for
that purpose.
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how often should instruments be calibrated
How often should
instruments be calibrated
P
lants can improve their efficiency and reduce costs by performing
calibration history trend analysis. By doing it, a plant is able
to define which instruments can be calibrated less frequently
and which should be calibrated more frequently. Calibration
history trend analysis is only possible with calibration software
that provides this functionality.
Adjusting calibration intervals based on history trend analysis
Manufacturing plants need to be absolutely confident that their
instrumentation products – temperature sensors, pressure transducers,
flow meters and the like – are performing and measuring to specified
tolerances. If sensors drift out of their specification range, the
consequences can be disastrous for a plant, resulting in costly production
downtime, safety issues or possibly leading to batches of inferior quality
goods being produced, which then have to be scrapped.
Most process manufacturing plants will have some sort of
maintenance plan or schedule in place, which ensures that all
instruments used across the site are calibrated at the appropriate times.
However, with increasing demands and cost issues being placed on
manufacturers these days, the time and resources required to carry
out these calibration checks are often scarce. This can sometimes lead
to instruments being prioritised for calibration, with those deemed
critical enough receiving the required regular checks, but for other
sensors that are deemed less critical to production, being calibrated
less frequently or not at all.
Plants can improve their
efficiencies and reduce
costs by using calibration
‘history trend analysis’,
a function available within
Beamex® CMX calibration
software.
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how often should instruments be calibrated
Sensors that are found
to be highly stable do not
need to be re-calibrated
as often as sensors that
tend to drift.
90
But plants can improve their efficiencies and reduce costs by
using calibration ‘history trend analysis’, a function available within
Beamex® CMX calibration software. With this function, the plant
can analyze whether it should increase or decrease the calibration
frequency for all its instruments.
Cost savings can be achieved in several ways. First, by calibrating
less frequently where instruments appear to be highly stable according
to their calibration history. Second, by calibrating instruments more
often when they are located in critical areas of the plant, ensuring
that instruments are checked and corrected before they drift out
of tolerance. This type of practise is common in companies that
employ an effective ‘Preventive Maintenance’ regime. The analyses
of historical trends and how a pressure sensor, for example, drifts in
and out of tolerance over a given time period, is only possible with
calibration software that provides this type of functionality.
Current practices in process plants
But in reality, how often do process plants actually calibrate their
instruments and how does a maintenance manager or engineer know
how often to calibrate a particular sensor?
In March 2010, Beamex conducted a survey that asked process
manufacturing companies how many instruments in their plant
required calibrating and the frequency with which these instruments
had to be calibrated. The survey covered all industry sectors, including
pharmaceuticals, chemicals, power and energy, manufacturing,
service, food and beverage, oil and gas, paper and pulp.
Interestingly, the survey showed that from all industry sectors, 56%
of the respondents said they calibrated their instruments no more
than once a year.
However, in the pharmaceuticals sector, 59% said they calibrated
once a year and 30% said they calibrated twice a year.
Perhaps unsurprisingly, due to it being a highly regulated industry,
the study proved also that the pharmaceuticals sector typically
possesses a significantly higher number of instruments per plant
that require calibrating. In addition, these plants also calibrate their
instruments more frequently than other industry sectors.
how often should instruments be calibrated
The benefits of analyzing calibration history trends
But regardless of the industry sector, by analysing an instrument’s
drift over time (ie. the historical trend) companies can reduce
costs and improve their efficiencies. Pertti Mäki is Area Sales
Manager at Beamex. He specialises in selling the Beamex® CMX
to different customers across all industry sectors. He comments:
“The largest savings from using the History Trend Option are in the
pharmaceuticals sector, without doubt, but all industry sectors can
benefit from using the software tool, which helps companies identify
the optimal calibration intervals for instruments.”
The trick, says Mäki, is determining which sensors should be recalibrated after a few days, weeks, or even years of operation and which
can be left for longer periods, without of course sacrificing the quality
of the product or process or the safety of the plant and its employees.
Doing this, he says, enables maintenance staff to concentrate their
efforts only where they are needed, therefore eliminating unnecessary
calibration effort and time.
But there are other, perhaps less obvious benefits of looking at the
historical drift over time of a particular sensor or set of measuring
instruments. As Mäki explains: “When an engineer buys a particular
sensor, the supplier provides a technical specification that includes details
on what the maximum drift of that sensor should be over a given time
period. With CMX’s History Trend Option, the engineer can now verify
that the sensor he or she has purchased, actually performed within the
specified tolerance over a certain time period. If it hasn’t, the engineer
now has data to present to the supplier to support his findings.”
But that’s not all. The History Trend function also means that a
plant can now compare the quality or performance of different sensors
from multiple manufacturers in a given location or set of process
conditions. This makes it an invaluable tool for maintenance or quality
personnel who, in setting up a new process line for example, can use
the functionality to compare different sensor types to see which one
best suits the new process.
Calibration software such as CMX can also help with the planning
of calibration operations. Calibration schedules take into account
the accuracy required for a particular sensor and the length of time
during which it has previously been able to maintain that degree of
accuracy. Sensors that are found to be highly stable do not need to be
re-calibrated as often as sensors that tend to drift.
The function enables
users to plan the optimal
calibration intervals for
their instruments.
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how often should instruments be calibrated
History Trend displays
the instrument’s drift
over a given period
both numerically
and graphically.
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The History Trend function enables users to plan the optimal
calibration intervals for their instruments. Once implemented,
maintenance personnel, for example, can analyze an instrument’s drift
over a certain time period. History Trend displays the instrument’s
drift over a given period both numerically and graphically. Based on
this information, it is then possible to make decisions and conclusions
regarding the optimal calibration interval and the quality of the
instruments with respect to measurement performance.
The ‘History Trend’ window enables users to view key figures of
several calibration events simultaneously, allowing to evaluate the
calibrations of a position or a device for a longer time period compared
to the normal calibration result view.
For example, the user can get an overview of how a particular device
drifts between calibrations and also whether the drift increases with
time. Also, the engineer can analyze how different devices are suited
for use in a particular area of the plant or process.
Reporting is straightforward and the user can even tailor the reports
to suit his or her individual needs, using the ‘Report Design’ tool
option.
how often should instruments be calibrated
CALIBRATION HISTORY TREND ANALYSIS
Calibration history trend analysis allows you to analyze the
instrument’s drift over a certain time period.
The graphical display
of the history trend
helps in visualizing and
optimizing the calibration
interval for the
instruments.
HISTORY TREND REPORT
HISTORY TREND USER-INTERFACE
• The Beamex® CMX stores every calibration event into the
database; the history trend is made automatically without any
extra manual work.
• The Beamex® CMX also indicates when new devices have
been installed and calibrated. This helps in comparing
differences between devices.
• The graphical display of the history trend helps in visualizing
and optimizing the calibration interval for the instruments.
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how often should instruments be calibrated
SUMMARY
The benefits of calibration history trend analysis:
• Analyzing and determining the optimal calibration interval for
instruments
• Conclusions can be made regarding the quality of a particular
measuring instrument
• Time savings: faster analyses is possible when compared to
traditional, manual methods
• Enables engineers to check that the instruments they have
purchased for the plant are performing to their technical
specifications and are not drifting out of tolerance regularly
• Supplier evaluation: the performance and quality of different
sensors from different manufacturers can be compared
quickly and easily.
When calibration frequency can be decreased:
• If the instrument has performed to specification and the drift
has been insignificant compared to its specified tolerance
• If the instrument is deemed to be non-critical or in a low
priority location
When calibration frequency should be increased:
• If the sensor has drifted outside of its specified tolerances
during a given time period
• If the sensor is located in a critical process or area of the
plant and has drifted significantly compared to its specified
tolerance over a given time period
• When measuring a sensor that is located in an area of the
plant that has high economic importance for the plant
• Where costly production downtime may occur as a result of
a ‘faulty’ sensor
• Where a false measurement from a sensor could lead to
inferior quality batches or a safety issue
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how often should instruments be calibrated
ISO 9001:2008 quality management requirements
7.6 Control of monitoring and measuring devices
The organization shall determine the monitoring and
measurement to be undertaken and the monitoring and
measuring devices needed to provide evidence of conformity of
product to determined requirements.
The organization shall establish processes to ensure that
monitoring and measurement can be carried out and are carried
out in a manner that is consistent with the monitoring and
measurement requirements.
Where necessary to ensure valid results, measuring equipment
shall
a) be calibrated or verified at specified intervals, or prior to use,
against measurement standards traceable to international or
national measurement standards; where no such standards
exist, the basis used for calibration or verification shall be
recorded;
b) be adjusted or re-adjusted as necessary;
c) be identified to enable the calibration status to be determined;
d) be safeguarded from adjustments that would invalidate the
measurement result;
e) be protected from damage and deterioration during handling,
maintenance and storage.
In addition, the organization shall assess and record the validity
of the previous measuring results when the equipment is found
not to conform to requirements.
The organization shall take appropriate action on the
equipment and any product affected.
Records of the results of calibration and verification shall be
maintained (see 4.2.4).
When used in the monitoring and measurement of specified
requirements, the ability of computer software to satisfy the
intended application shall be confirmed. This shall be undertaken
prior to initial use and reconfirmed as necessary.
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how often should calibrators be calibrated
How often should
calibrators be calibrated
A
s a general rule for Beamex’s documenting MC calibrators,
starting with a 1-year calibration period is recommended,
because the calibrators has a 1-year uncertainty specified.
The calibration period can be changed in the future, once you
begin receiving cumulated stability history, which is then compared
to the uncertainty requirements. In any case, there are many issues
to be considered when deciding a calibrator’s calibration period, or
the calibration period for any type of measuring device. This article
discusses some of the things to be considered when determining the
calibration period, and provides some general guidelines for making
this decision. The guidelines that apply to a calibrator, also apply to
other measuring equipment in the traceability chain. These guidelines
can also be used for process instrumentation.
An important aspect to consider when maintaining a traceable
calibration system is to determine how often the calibration equipment
should be recalibrated. International standards (such as ISO9000,
ISO10012, ISO17025, CFRs by FDA, GMP, etc.) require the use
of documented calibration programs. This means that measuring
equipment should be calibrated traceably at appropriate intervals and
that the basis for the calibration intervals should be evaluated and
documented.
When determining an appropriate calibration period for any
measuring equipment, there are several things to be considered. They
are discussed below.
Uncertainty need is
one of the most important
things to consider when
determining the calibration
period.
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how often should calibrators be calibrated
Uncertainty need
One of the first things to evaluate is the uncertainty need of the
customer for their particular measurement device. Actually, the initial
selection of the measurement device should be also done based on this
evaluation. Uncertainty need is one of the most important things to
consider when determining the calibration period.
Stability history
In critical applications,
the costs of an outof-tolerance situation
can be extremely high
(e.g. pharmaceutical
applications) and therefore
calibrating the equipment
more often is safer.
When the customer has evaluated his/her needs and purchased suitable
measuring equipment, (s)he should monitor the stability history of the
measuring equipment. The stability history is important criteria when
deciding upon any changes in the calibration period. Comparing the
stability history of measuring equipment to the specified limits and
uncertainty needs provides a feasible tool for evaluating the calibration
period. Naturally, calibration management software with the history
analysis option is a great help in making this type of analysis.
The cost of recalibration vs. consequences
of an out-of-tolerance situation
Optimizing between recalibration costs and the consequences of an outof-tolerance situation is important. In critical applications, the costs of
an out-of-tolerance situation can be extremely high (e.g. pharmaceutical
applications) and therefore calibrating the equipment more often is
safer. However, in some non-critical applications, where the out-oftolerance consequences are not serious, calibration can be made less
frequently. Therefore, evaluating of the consequences of an out-oftolerance situation is something to be considered. The corrective actions
in such a case should also be made into an operating procedure.
Some measurements in a factory typically have more effect on a
product quality than others, and therefore some measurements are
more acute than others and should be also calibrated more often than
others.
Initial calibration period
When you purchase calibration equipment with which you are not
familiar, you still need to decide the initial calibration period. In this
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how often should calibrators be calibrated
situation, abiding by the manufacturer’s recommendation is best. For
more acute applications, using a shorter calibration period right from
the beginning is recommended.
Other things to be considered
There are also other issues to be considered when determining
the calibration period, such as the workload of the equipment,
the conditions where the equipment will be used, the amount of
transportation and is the equipment look damaged.
In some cases, crosschecking with other similar measuring
equipment is also feasible for detecting the need for calibration.
Crosschecking may be carried out before every measurement in some
acute applications.
Naturally, only appropriate, metrological, responsible personnel
in the company may make changes to the calibration equipment’s
calibration period.
In some cases,
crosschecking with
other similar measuring
equipment is also feasible
for detecting the need
for calibration.
SUMMARY
The main issues to be considered when determining the
calibration period for measuring equipment should include at
least following:
• The uncertainty needs of the measurements
to be done.
• The stability history of the measuring equipment.
• Equipment manufacturer’s recommendations.
• The risk and consequences of an out-of-tolerance situation.
• Acuteness of the measurements.
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paperless calibration improves quality and cuts costs
Paperless calibration improves
quality and cuts costs
P
aper is part of our everyday lives – whether in the workplace or
at home. Take a minute to look around the room you are in and
you’ll notice how many objects are made from paper: books,
magazines, printer paper, perhaps even a poster on the wall.
Global consumption of paper has grown 400% in the last 40 years.
Today, almost 4 billion trees or 35% of the total trees cut down across
the world are used in paper industries on every continent (source: www.
ecology.com).
So let’s not add to this already heavy burden on our forests and
the environment. As manufacturing companies, our consumption of
paper is far higher than it needs to be, especially given that there are
technologies, software and electronic devices readily available today
which render the use of paper in the workplace unnecessary.
Other than helping to save our planet and reducing the number of
trees cut down each year, as businesses, there are other, significant
benefits in minimising the use of paper.
Take the calibration of plant instrumentation devices such as
temperature sensors, weighing instruments and pressure transducers.
Globally, amongst the process manufacturing industries, calibrating
instruments is an enormous task that consumes vast amounts of
paperwork. Far too many of these companies still use paper-based
calibration systems, which means they are missing out on the benefits
of moving towards a paperless calibration system.
Far too many of these
companies still use
paper-based calibration
systems, which means
they are missing out on
the benefits of moving
towards a paperless
calibration system.
Traditional paper-based calibration systems
Typically, a paper-based calibration system involves the use of handwritten documents. Whilst out in the field, a maintenance or service
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paperless calibration improves quality and cuts costs
With paperless
systems, workflow
improves dramatically.
engineer will typically use a pen and paper to record instrument
calibration results. On returning to the office, these notes are then
tidied up and/or transferred to another paper document, after which
they are archived as paper documents.
While using a manual, paper-based system requires little or no
investment in new technology or IT systems, it is extremely labourintensive and means that historical trend analysis of calibration results
becomes very difficult. In addition, accessing calibration data quickly
is not easy. Paper systems are time consuming, they soak up lots of
company resources and manual (typing) errors are commonplace. Dual
effort and the re-keying of calibration data into multiple databases
become significant costs to the business.
These same companies that use paper-based calibration systems
are together generating hundreds of thousands (millions?) of paper
calibration certificates each year. However, by utilising the latest
software-based calibration management systems from companies
like Beamex, these organisations can significantly reduce their paper
consumption, whilst also improving quality, workflow and making
other significant cost savings for the business.
Practical benefits of using less paper
Aside from the financial benefits of moving towards a paperless
calibration system, there are practical reasons why firms should go
paperless. Often, in industrial environments, it is not practicable to
store or carry lots of paperwork. After all, every square foot of the
business has an associated cost.
Furthermore, important paper records could potentially be lost
or damaged in an accident or fire. So why would these companies
generate and store separate paper copies of important records such as
works orders, standard operating procedures (SOPs), blank calibration
certificates, etc. when these records can all be combined into a single
electronic record?
Improved workflow
With paper-based systems, paper records that need approval have to be
routed to several individuals, which is time-consuming. With paperless
systems, workflow improves dramatically. There will be less waiting
time, as those individuals who need to sign off records or calibration
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paperless calibration improves quality and cuts costs
documents can share or access electronic records simultaneously from
a central database. The cost and time associated with printing copies
of paper documents is also eliminated, as well as the cost of filing and
storing those paper records.
Just as important, electronic records enable easier analysis of data,
particularly calibration results. Historical trending becomes easier,
faster and more reliable, which again has cost reduction benefits to the
business. Calibration intervals can be optimised. For example, those
instruments that are performing better than expected may well justify
a reduction in their calibration frequency.
When a plant is being audited, calibration software facilitates both
the preparation and the audit itself. Locating records and verifying
that the system works becomes effortless when compared to traditional
paper-based record keeping. Paperless calibration systems improve
plant efficiencies because the entire calibration process is now
streamlined and automated. Costly production downtime due to
unforeseen instrument failures will also be reduced.
Data integrity
Paperless calibration
systems improve plant
efficiencies because the
entire calibration process
is now streamlined and
automated.
The integrity of paper-based calibration systems cannot be relied
upon. Paper records may not always reflect the truth. For example,
manual errors such as misreadings can occur, particularly when using
weighscales or other instruments that are open to an individual’s
own interpretation of the data. Sometimes users may inappropriately
modify the results data due to work pressures or lack of time/resources.
Illegible handwritten notes are also a problem, especially if these
paper records need to be typed or transcribed to a computer system
or database. Transcription errors such as these can lead to all sorts of
problems for a business and can take months to rectify or to identify
the rogue data.
Business benefits
For those more enlightened companies that use software-based
calibration systems, the business benefits are significant. The whole
calibration process – from initial recording of calibration data through
to historical trend analysis – will take less time, whilst mistakes and
manual errors will be virtually eliminated. In turn, this means that
operators, engineers and management will have more confidence in
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paperless calibration improves quality and cuts costs
the data, particularly when it comes to plant audits. In addition, this
greater confidence in calibration data leads to a better understanding
and analysis of business performance and KPIs (particularly if the
calibration software is integrated with other business IT systems such
as a CMMS) leading to improved processes, increased efficiencies and
reduced plant downtime.
Commissioning
The calibration data
is shared with other
business IT systems
electronically, resulting
in completely paperless,
end-to-end workflows.
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At plant commissioning times, electronic records simplify
the handover of plant and equipment. Although handover by
commissioning teams that use paper records is straightforward and
of universal format, electronic records are easy to manipulate and can
be re-used in different IT systems. Electronic data also provides an
excellent foundation for ongoing plant operation and maintenance,
without needing to collect all the plant data again.
How paperless should you go?
Of course, in reality, many companies are neither completely paperless
nor rely solely on paper-based systems – the process is sometimes
a hybrid of the two. A key part of paperless calibration records is
the capture of data at point of work, often in difficult industrial
environments that would make the use of portable office computers
impractical, and the manual entry of calibration results into unintelligent calibration forms on portable industrial computers prone
to eye-to-hand data mis-reads and repetitive strain induced error. One
way to overcome these error prone data capture methods is to use
portable documenting calibrators to measure what can be measured
and provide intelligent, technician friendly interfaces on industrialized
PDA or tablet based hardware when manual data entry cannot be
avoided. The un-editable electronic data stored on high performance
multifunction calibrators can be uploaded to calibration management
software for safe storage and asset management. Companies can go
even further than this and use electronic records for works orders,
business management systems, data historians, and for control
systems. In other words, the calibration data is shared with other
business IT systems electronically, resulting in completely paperless,
end-to-end workflows.
paperless calibration improves quality and cuts costs
Suitable hardware
Rather than rely on engineers in the field accurately keying in
calibration results into suitably robust laptops or PDAs, it is better to
source the data electronically using documenting calibrators that are
specifically designed for this task.
Validation, training & education
Paperless systems also need validating in the user’s own environment.
Here, Beamex provides comprehensive validation, education and
training services for customers.
Education and training for users is critical, as this will help companies
to overcome the natural resistance to change amongst the workforce,
which may be used to dealing with traditional, paper-based systems.
Case study
Beamex is helping many organisations to implement paperless
calibration management systems, including Pharmaceuticals,
Chemicals, Power & Energy, Oil Gas & Petrochemicals companies.
Amongst these customers is UK firm Croda Chemicals Europe.
Based in East Yorkshire near Goole, the Croda plant uses pressurised
vessels to purify lanolin for healthcare and beauty products. Each
vessel needs to be certified at least once every two years in order
to demonstrate that the vessel is safe and structurally sound. This
includes a functionality check on all of the pressure instrumentation,
as well as the sensors that monitor the incoming chemical additives
and the outgoing effluent.
Senior Instrument Technician David Wright recalls what it was like
to perform all of those calibration operations with paper and pencil
during the company’s regularly scheduled maintenance shutdowns:
“It took us one week to perform the calibrations and a month to put
together the necessary paperwork.”
Today, Croda uses the CMX calibration management software
system from Beamex, which coordinates data collection tasks and
archives the results. “It’s faster, easier and more accurate than our old
paper-based procedures,” says Wright. “It’s saving us around 80 manhours per maintenance period and should pay for itself in less than
three years.”
Education and training
for users is critical, as
this will help companies
to overcome the natural
resistance to change
amongst the workforce,
which may be used to
dealing with traditional,
paper-based systems.
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intelligent commissioning
Intelligent commissioning
C
alibration plays a vital role in process plant commissioning and
when installing new instruments. This article explains process
instrument commissioning and the benefits of calibration
during the commissioning phase.
What is process instrument commissioning?
Successful commissioning
of process instrumentation
must be considered within
the context of the overall
commissioning program.
Successful commissioning of process instrumentation is an essential
requirement for ideal plant performance. A plant, or any defined part
of a plant, is ready for commissioning when the plant has achieved
mechanical completion. Plant commissioning involves activities such
as checking to ensure plant construction is complete and complies with
the documented design or acceptable (authorized and recorded) design
changes. In general, commissioning activities are those associated with
preparing or operating the plant or any part of the plant prior to the
initial start-up and are frequently undertaken by the owner or joint
owner/ contractor team.
Commissioning may involve mock operations which are
commissioning activities conducted to allow operational testing
of the equipment and operator training and familiarization. At
the completion of commissioning, the plant will be fully ready for
production operation.
Energizing power systems, operational testing of plant equipment,
calibration of instrumentation, testing of the control systems as well as
verification of the operation of all interlocks and other safety systems
are also typical commissioning tasks. These activities are usually
described as ‘cold commissioning’.
Pre-commissioning activities are those which have to be undertaken
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intelligent commissioning
There are many reasons
why instruments should
be calibrated during the
commissioning phase
before start-up.
prior to operating equipment, such as adjustments and checks
on machinery performed by the construction contractor prior to
commissioning and without which the installation cannot be said to
be mechanically complete. Mechanical completion of a plant or any
part of a plant occurs when the plant or a part of the plant has been
completed in accordance with the drawings and specifications, and the
re-commissioning activities have been completed to the extent where
the owner approves the plant and can begin commissioning activities.
Commissioning requires a team of people with a background in
plant design, plant operation and plant maintenance. Some companies
employ specialized commissioning engineers. This can prove to be a
worthwhile investment for large plants because it allows for dedicated
responsibility and focus in operations and significant improvements to
schedules, and adverse incidents at the start-up phase can be avoided.
An extra day taken for commissioning means the same to the plant
owner as an extra day taken during designing or construction; in fact, it
may cost more, as the plant owner’s commitments in terms of product
marketing and operational costs are likely to be higher.
Management, personnel and cost of commissioning
Since commissioning takes place toward the end of the project, there
is a risk that the work may be under-resourced, because the funds have
been allotted to cover budget overruns. It is essential to comprehend
the scope and length of commissioning activities and include them
in the initial project plan and budget allocations, and ensure this
commitment is maintained.
The cost of process instrument commissioning is typically affected
by the following issues: learning and familiarizing with the field device,
physically installing the field device, connecting to and identifying
the field device, configuring the required parameters and testing the
configuration and interface to other systems. Basically, these steps must
be repeated with every field device that will be installed at the plant.
As there are many cost factors in the commissioning process,
detailed planning of commissioning and plant handover are essential
elements of the overall project plan and schedule as any other grouping
of activities.
Each of the commissioning activities must be broken down into a
number of manageable tasks, and a schedule needs to be established
for each task including benchmarks for monitoring purposes. The rate
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intelligent commissioning
Construction
Pre-commissioning
Mechanical completion
Commissioning
Trial operation
Initial start-up
Examine product specification
Examine production performance
Acceptance of plant
Sequence of activities leading to commissioning and acceptance of a
plant.
The calibration database
can be calibration
software designed
specifically for managing
calibration assets and
information, such as the
Beamex® CMX Calibration
Software.
of commissioning is measurable (e.g. number of loops or sequence
of steps tested per day), thereby enabling progress to be reviewed
regularly.
Successful commissioning of process instrumentation must be
considered within the context of the overall commissioning program.
Good planning, coordination, communications, documentation,
teamwork and training are all essential. The commissioning team
consists of a mixture of specialists, instrument and process engineers,
and the size of the team and composition of specialists depends on
the nature and scope of the system.
Calibration and the commissioning of field instrumentation
New process instrumentation is typically configured and calibrated by
the manufacturer prior to installation. However, instruments are often
recalibrated upon arrival at the site, especially if there has been obvious
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intelligent commissioning
damage in transit or storage. There are also many other reasons why
instruments should be calibrated during the commissioning phase
before start-up.
Assuring transmitter quality
First of all, the fact that an instrument or transmitter is new does
not automatically mean that it is within required specifications.
Calibrating a new instrument before installing or using it is a quality
assurance task. You can check the overall quality of the instrument to
see if it is defective and to ensure it has the correct, specified settings.
Reconfiguring a transmitter
The trick is determining
which sensors should be
recalibrated after a few
hours, weeks, or years
of operation and which
can be left as is for longer
periods without sacrificing
quality or safety.
The new uninstalled instrument or transmitter may have the correct,
specified settings. However, it is possible that the original planned
settings are not valid anymore and they need to be changed. By
calibrating an instrument you can check the settings of the instrument.
After you have performed this task, it is possible to reconfigure
the transmitter, when the initial planned specifications have been
changed. Calibration is therefore a key element in the process of
reconfiguring an uninstalled transmitter.
Monitoring the quality and stability of a transmitter
When calibration procedures are performed for an uninstalled
instrument, the calibration serves also future purposes. By calibrating
the transmitter before installation and on a regular basis thereafter, it
is possible to monitor the stability of the transmitter.
Entering the necessary transmitter data into a calibration database
By calibrating an instrument before installation it is possible to
enter all the necessary instrument data into the calibration database,
as well as to monitor the instrument’s stability, as was explained in
the previous paragraph. The calibration database can be calibration
software designed specifically for managing calibration assets and
information, such as the Beamex® CMX Calibration Software. The
transmitter information is critical in defining the quality of the
instrument and for planning the optimal calibration interval of the
instrument. Transmitters that are found to be highly stable need
not be recalibrated as often as transmitters that tend to drift. The
trick is determining which sensors should be recalibrated after a few
hours, weeks, or years of operation and which can be left as is for
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intelligent commissioning
longer periods without sacrificing quality or safety. Doing so allows
maintenance personnel to concentrate their efforts only where needed,
thereby eliminating unnecessary calibration work. Therefore, entering
the instrument data into a calibration management system is part of
the calibration procedures performed on an instrument before it is
installed and in use.
Integrated calibration solution by Beamex
The Beamex® Integrated Calibration Solution, consisting of calibration
software and documenting calibration equipment, improves the
quality and efficiency of the entire calibration system through faster,
smarter and more accurate management of all calibration assets and
procedures.
The Beamex® MC series documenting calibrators can be used for
calibrating pressure, temperature, electrical and frequency signals. The
Beamex calibrators support various different transmitter protocols,
such as analog, HART, Foundation Fieldbus and Profibus. The Beamex
calibrators are all-in-one calibrators, which mean that they can be used
to replace several individual measurement devices. Intrinsically safe
calibrators for potentially explosive environments are also available.
The Beamex® CMX Calibration Software can be used for improving
the quality, productivity and cost-effectiveness of a plant’s calibration
process. The Beamex® CMX can be used for planning and scheduling
calibrations, managing and storing all calibration data as well as
analyzing and optimizing the calibration interval. Using the CMX
gives always a clear status of the transmitters; for instance, are they
installed and ready for calibration, does anyone perform the calibration
(check in/out function) and what is the instrument/position status
(pass/fail).
Having a fully integrated calibration management system – using
documenting calibrators and calibration management software
– is important. Beamex® CMX Calibration Software ensures
that calibration procedures are carried out at the correct time and
that calibration tasks do not get forgotten, overlooked or become
overdue. By using a documenting calibrator, the calibration results
are stored automatically in the calibrator’s memory during the
calibration process. Engineers performing calibrations no longer
have to write down any results on paper, making the entire process
much quicker and reducing costs. All calibration documentation is
Beamex® CMX Calibration
Software ensures that
calibration procedures are
carried out at the correct
time and that calibration
tasks do not get forgotten,
overlooked or become
overdue.
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intelligent commissioning
By using a documenting
calibrator, the calibration
results are stored
automatically in the
calibrator’s memory
during the calibration
process.
therefore automatically produced when using the Beamex® Integrated
Calibration Solution. The quality and accuracy of calibration results
also improve, as there are fewer mistakes due to human error. The
calibration results are transferred automatically from the calibrator’s
memory to the computer/ database. This means that engineers do not
spend their time transferring the results from their notepad to final
storage on a computer; again, saving time and money.
Major time-savings can also be achieved by using Beamex’s
documenting MC calibrators HART and/or Fieldbus functionality
to enter transmitter data into the calibrators’ memory where the data
can be populated to the CMX Calibration Software, instead of typing
the data manually into the calibration database.
SUMMARY
Calibration is beneficial during process plant commissioning
for various different reasons:
• Transmitter quality assurance
• Reconfiguring a transmitter
• Monitoring the quality and stability of a transmitter
• Entering the necessary transmitter data into a calibration
database and defining the optimal calibration interval
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113
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successfully executing a system integration project
Successfully executing a system
integration project
F
or process manufacturers today, having a reliable, seamlessly
integrated set of IT systems across the plant, or across multiple
sites, is critical to business efficiency, profitability and growth.
Maintaining plant assets – whether that includes production line
equipment, boilers, furnaces, special purpose machines, conveyor
systems or hydraulic pumps – is equally critical for these companies.
Maintenance management has become an issue which deserves
enterprise-wide and perhaps multi-site attention, especially if the
company is part of an asset-intensive industry, where equipment and
plant infrastructure is large, complex and expensive. If stoppages
to production lines due to equipment breakdowns are costly,
implementing the latest computerized maintenance management
systems (CMMS) might save precious time and money.
In the process industries, a small, but critical part of a company’s
asset management strategy should be the calibration of process
instrumentation. Manufacturing plants need to be sure that their
instrumentation products – temperature sensors, pressure transducers,
flow meters and the like – are performing and measuring to specified
tolerances. If sensors drift out of their specification range, the
consequences can be disastrous, perhaps resulting in costly production
downtime, safety issues or batches of inferior quality goods being
produced, which then have to be scrapped. For this, Beamex’s
calibration management software, Beamex® CMX, has proved
itself time and time again across many industry sectors, including
pharmaceuticals, chemicals, nuclear, metal processing, paper, oil and
gas.
In the process industries,
a small, but critical
part of a company’s
asset management
strategy should be the
calibration of process
instrumentation.
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successfully executing a system integration project
Seamless communication
Beamex® CMX
Professional or Beamex®
CMX Enterprise software
can easily be integrated
to CMM systems,
whether it is a Maximo,
SAP or Datastream
CMM system or even a
company’s own, in-house
software for maintenance
management.
Today, most process manufacturers use some sort of computerized
maintenance management system (CMMS) that sits alongside
their calibration management system. Beamex® CMX Professional
or Beamex® CMX Enterprise software can easily be integrated to
CMM systems, whether it is a Maximo, SAP or Datastream CMM
system or even a company’s own, in-house software for maintenance
management.
Beamex® CMX helps companies document, schedule, plan, analyze
and optimize their calibration work. Seamless communication between
CMX and ‘smart’ calibrators means that companies have the ability to
automate predefined calibration procedures. As well as retrieving and
storing calibration data, CMX can also download detailed instructions
for operation before and after calibrating, like procedures, reminders
and safety-related information. Seamless communication with
calibrators also provides many practical benefits such as a reduction
in paperwork, elimination of human error associated with manual
recording, and the ability to speed up the calibration task. CMX also
stores the complete calibration history of process instruments and
produces fully traceable calibration records.
Integrating CMX with a CMM system means that plant hierarchy
and all work orders for process instruments can be generated and
maintained in the customer’s CMM system. Calibration work
orders can easily be transferred to CMX Calibration Software. Then,
once the calibration work order has been executed, CMX sends an
acknowledgement order of this work back to the customer’s CMM
system. All detailed calibration results are stored and available on the
CMX database.
Integration project
A customer may have a large CMM system and a considerable amount
of data keying to perform before integration is complete. A data
exchange module or interface that sits between the two systems is
required. The integration project involves three main parties: Beamex,
the customer and the CMM system software partner.
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successfully executing a system integration project
Project organization and resourcing
In order to have a successful integration, it’s important that the right
people and decision-makers are involved and participate right from
the beginning of the project. It’s also essential that the main roles and
responsibilities of the parties are specified before the project evolves.
Moreover, a project organization should be established and include
members from both the supplier’s and the customer’s organization,
as a successful project requires input from both parties. The role of
each member should be defined and project managers appointed. The
project manager is usually responsible for the operative management
of the project. In addition, a project steering group may need to be
established. The project steering group is responsible for making key
decisions during the project. The role, tasks and authority of the
project steering group must be defined as well as the decision-making
procedures.
Project phases
The integration project is divided into four main phases:
The integration project
involves three main
parties: Beamex, the
customer and the CMM
system software partner.
1. Scope of Work
2. Development and Implementation
3. Testing
4. Installation, Verification and Training
The four main phases are also often divided into sub-phases. A
schedule is usually defined for the completion of the entire project as
well as for the completion of each project phase. Each project phase
should be approved according to the acceptance procedures defined
in the offer, agreement, project plan or other document annexed to
the offer / agreement.
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successfully executing a system integration project
Scope of work
To ensure successful integration with a satisfied customer, defining
the correct scope of work (SOW) is crucial. The scope of work should
include a brief project description, services provided, main roles,
partner responsibilities and the desired outcome. The scope of work
is important to make sure that both the supplier and the customer
have understood the project in question and they have similar
expectations from it. The SOW is often developed through pre-studies
and workshops.
Defining what is not included in the scope of work is just as important
as defining what is included in it. This means that establishing some
framework and limitations for the project are also very important,
as the resourcing, scheduling and costs of the project depend greatly
on the scope of work. If the scope of work is not defined carefully,
questions or problems may appear later in the project, which will direct
the project back to phase one where a review of the scope is necessary.
This is an urgent but time-consuming matter and can be avoided if
the right people and decision-makers participate in the first project
phase. However, as changes to the original scope of work may be
necessary and required even in projects where the SOW phase has
been done carefully, it is important that the supplier and customer
agree on change management procedures as early as the starting phase
of the project.
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successfully executing a system integration project
Development and implementation
When the scope of work has been defined and approved by both
parties, the integration can enter the next phase, which is the actual
development and implementation of the project deliverables.
Testing
Testing occurs both during the project after each partial delivery, in
order to be able to continue the development work to next phase, and
at the final stage of the project. The testing, approval procedures and
timelines should be defined when agreeing on the project.
Installation, verification and training
The final stage in the integration process is the installation and testing
at the customer’s facility and taking the system into production use.
The project manager at the buyer’s facility now plays a major role in
the success of the integration process. The supplier will, if required
and agreed, assist with informing, training and providing training
materials.
When the integration is finished, the customer has a system that
saves time, reduces costs and increases productivity by preventing
unnecessary double effort and re-keying of procedures in separate
INTEGRATION PROJECT PHASES
• Purpose / needs
• Target
• Supplier’s responsibilities
• Customer’s responsibilities
• Project management and
project steering group
• Change management
• Testing and acceptance
procedures
Scope of
work
(SOW)
Specifications
documentation
Development
and
implementation
Implementation
documentation
Testing
Testing
documentation
Installation
Verification
Training
Instructional
documentation
When the integration is
finished, the customer
has a system that saves
time, reduces costs and
increases productivity by
preventing unnecessary
double effort and rekeying of procedures in
separate systems.
• Final approval by customer
FOLLOW UP
CLOSURE OF INTEGRATION PROJECT
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successfully executing a system integration project
Integrating a CMM
system with calibration
management software
is an important step in
the right direction when it
comes to EAM, Enterprise
Asset Management.
120
systems. When there is no need to manually re-key the data, typing
errors are eliminated. A CMMS integration will enable the customer
company to automate its’ management with smart calibrators. This
improves the quality of the entire system.
Integrating a CMM system with calibration management software
is an important step in the right direction when it comes to EAM,
Enterprise Asset Management. However, EAM is more than just
maintenance management software. It’s about companies taking a
business-wide view of all their plant equipment and coordinating
maintenance activities and resources with other departments and
sites, particularly with production teams. Savings from EAM are
reasonably well-documented and come in various guises, the most
common benefits being: less equipment breakdowns (leading to a
reduction in overall plant downtime); a corresponding increase in
asset utilization or plant uptime; better management of spare parts
and equipment stocks; more efficient use of maintenance staff; and
optimized scheduling of maintenance tasks and resources. But the
key to success is really the quality of information you put in the
software, the data has to be as close to 100% accurate as possible to
get maximum benefit from the system.
121
Calibration
in Industrial
Applications
124
the benefits of using a documenting calibrator
The benefits of using
a documenting calibrator
F
or process manufacturers, regular calibration of instruments
throughout a manufacturing plant is common practice. In plant
areas where instrument accuracy is critical to ensure product
quality, safety or custody transfer, calibration every six months – or
even more frequently – is not unusual.
However, the key final step in any calibration process – documentation
– is often neglected or overlooked because of a lack of resources, time
constraints or the pressure of everyday activities. Indeed, many process
plants are under pressure to calibrate instruments quickly but accurately
and to ensure that the results are then documented for quality assurance
purposes and to provide full traceability.
The purpose of calibration itself is to determine how accurate an
instrument or sensor is. Although most instruments are very accurate
these days, regulatory bodies often need to know just how inaccurate a
particular instrument is and whether it drifts in and out of a specified
tolerance over time.
Many process plants
are under pressure to
calibrate instruments
quickly but accurately and
to ensure that the results
are then documented
for quality assurance
purposes and to provide
full traceability.
What is a documenting calibrator?
A documenting calibrator is a handheld electronic communication
device that is capable of calibrating many different process signals
such as pressure, temperature and electrical signals, including
frequency and pulses, and then automatically documenting the
calibration results by transferring them to a fully integrated calibration
management software. Some calibrators can read HART, Foundation
Fieldbus or Profibus output of the transmitters and can even be used
for configuring ‘smart’ sensors.
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the benefits of using a documenting calibrator
Heikki Laurila, Product Manager at Beamex in Finland comments,
“I would define a documenting calibrator as a device that has the dual
functionality of being able to save and store calibration results in its
memory, but which also integrates and automatically transfers this
information to some sort of calibration management software.”
A non-documenting calibrator is a device that does not store data,
or stores calibration data from instruments but is not integrated to a
calibration management system. Calibration results have to be keyed
manually into a separate database, spreadsheet or paper filling system.
Why use a documenting calibrator?
The engineer does
not have to write any
results down on paper,
which makes the entire
process much faster and
consequently reduces
costs.
126
By using a documenting calibrator, the calibration results are stored
automatically in the calibrator’s memory during the calibration
process. The engineer does not have to write any results down on
paper, which makes the entire process much faster and consequently
reduces costs. The quality and accuracy of calibration results will also
improve, as there will be fewer mistakes due to human error.
The calibration results are automatically transferred from the
calibrator’s memory to the computer/database. This means the
engineer does not have to spend time transferring the results from his
notepad to final storage on a computer; again, saving time and money.
With instrument calibration, the calibration procedure itself is
critical. Performing the calibration procedure in the same way each
time is important for the consistency of results. With a documenting
calibrator, the calibration procedure can be automatically transferred
from the computer to the handheld calibrator before going out into
the field.
As Laurila states, “Engineers, who are out in the field performing
instrument calibrations, receive instant pass or fail messages with a
documenting calibrator. The tolerances and limits for a sensor, as
well as detailed instructions on how to calibrate the transmitter, are
entered once into the calibration management software and then
downloaded to the calibrator. This means calibrations are carried out
in the same way every time because the calibrator tells the engineer
which test point he needs to measure next. Also, having an easy-touse documenting calibrator is definitely the way forward, especially
if calibration is one of the many tasks that the user has to carry out in
his daily maintenance routine.”
With a multi-functioning documenting calibrator, such as the
the benefits of using a documenting calibrator
Beamex® MC5 or MC6, the user doesn’t need to carry as much
equipment while out in the field. Both calibrators can be used also
to calibrate, configure and trim HART, Foundation Fieldbus H1 or
Profibus PA transmitters.
Laurila continues, “With a documenting calibrator, such as the
MC5 or the MC6, the user can download calibration instructions for
hundreds of different instruments into the device’s memory before
going out into the field. The corresponding calibration results for
these instruments can be saved in the device without the user having
to return to his PC in the office to download/upload data. This means
the user can work in the field for several days.”
Having a fully integrated calibration management system – using
documenting calibrators and calibration management software –
is important. Beamex® CMX Calibration Software ensures that
calibration procedures are carried out at the correct time and that
calibration tasks are not forgotten, overlooked or overdue.
Benefits in practice
Conventional calibration work relies on manual, paper-based
systems for documenting. Manual calibration takes more time and
is more prone to error. Oftentimes, the field engineer calibrates the
instrument, handwrites the results onto a paper form and then reenters this information into a database when he returns to the office.
Unintentional errors often occur and the whole process is timeconsuming.
Using Beamex® CMX Calibration Software and the documenting
Beamex® MC6 or MC5 Multifunction Calibrators provides full
control of the entire calibration process and reduces costs by up
to 50 %.* Why? Because the devices provide higher accuracy, the
calibration process is much faster, and the system provides full
traceability. When you’ve got to calibrate instruments throughout a
site, typically with five-point checks on each instrument, speed and
accuracy are critical. Using the MC6 or MC5 with CMX software
means that calibration instructions for an instrument and calibration
orders are downloaded to the calibrators and ready to guide the
engineer in the field with correct calibration procedures.
Calibration software
ensures that calibration
procedures are carried out
at the correct time and that
calibration tasks are not
forgotten, overlooked or
overdue.
___________________
* Reported to the Industrial Instrumentation and Controls Technology Alliance and presented
at the TAMU ISA Symposium, January, 2004
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the benefits of using a documenting calibrator
After completing instrument calibrations, the system provides a
full quality assurance report of all instruments calibrated along with a
required calibration certificate. This not only ensures full traceability
but also reflects full and traceable documentation of the completed
work.
SUMMARY
The benefits of using a documenting calibrator
Calibration results are
automatically transferred
from the calibrator’s
memory to a computer or
fully integrated calibration
management system.
128
• Calibration results are automatically stored in the
calibrator’s on-board memory during the calibration
procedure.
• Calibration results are automatically transferred from the
calibrator’s memory to a computer or fully integrated
calibration management system.
• Less paperwork and fewer manual errors.
• Reduced costs from a faster and more efficient calibration
process.
• Improved accuracy, consistency and quality of calibration
results.
• A fully traceable calibration system for the entire plant.
• The calibration procedure itself is guided by the calibrator,
which uploads detailed instructions from the computer or
calibration management software.
• No manual printing or reading of calibration instructions is
required; again, saving time and money and simplifying the
process.
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calibration of weighing instruments
part 1
Calibration of weighing instruments
Part 1
F
rom the point of view of the owner, weighing instruments, usually
called scales or balances, should provide the correct weighing
results. How the weighing instrument is used and how reliable the
weighing results are can be very different. Using weighing instruments
for legal purposes must have legal verification.
If a weighing instrument is used in a quality system, the user must
define the measurement capability of it. In any case, it is the owner
or the user of the instrument that carries the final responsibility of
measurement capability and who is also responsible for the processes
involved. (S)He must select the weighing instrument and maintenance
procedure to be used to reach the required measurement capability.
From a regulatory point of view, the quality of a weighing instrument
is already defined in OIML regulations, at least in Europe. Calibration
is a means for the user to obtain evidence of the quality of weighing
results, and the user must have the knowledge to apply the information
achieved through calibration.
In any case, it is the
owner or the user of
the instrument that carries
the final responsibility
of measurement
capability and who is
also responsible for the
processes involved.
Calibration and legal verification
Weighing instruments may also possess special features. One of these
features includes making measurements for which legal verification is
required, for example when invoicing is based on the weight of a solid
material. The features may vary slightly from country to country, but
in the EU they are the same, at least at the stage when the weighing
instrument is being introduced into use.
Verification and calibration abide by a different philosophy.
Calibration depicts the deviation between indication and reference
(standard) including tolerance, whereas verification depicts the
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calibration of weighing instruments
part 1
maximum permissible amount of errors of the indication. This is a
feasible practice for all weighing. The practical work for both methods
is very similar and both methods can be used to confirm measurement
capability, as long as legal verification is not needed. The terminology
and practices used previously for verifying measurement capability,
and for weighing technology in general, are based on these practices of
calibrating and verifying, even if it was a question of general weighing
(non-legal).
Confirmation is the collecting of information
We must remember
that the quality of the
evaluation of measuring
tolerance depends on
the collected information
through calibration.
132
Confirming the capability of weighing instruments should happen
by estimating the quality of the measuring device in the place where
it will be used. In practice, this means investigating the efficiency of
the weighing instrument; this operation is known as calibration (or
verification). One calibration provides information on a temporary
basis and a series of calibrations provides time-dependent information.
The method of calibration should be selected such that it provides
sufficient information for evaluating the required measuring tolerance.
The method should be precise for achieving comparable results during
all calibrations.
Comparing the indication of weighing instruments with a set
standard gives the deviation or error. However, to be able to define the
measuring tolerance, we need more information about the weighing
instrument, such as repeatability, eccentric load, hysteresis, etc. We
must remember that the quality of the evaluation of measuring
tolerance depends on the collected information through calibration.
Using a calibration program, which goes through the same steps for
every calibration – calculates deviation and measuring tolerance, and, if
necessary, produces a calibration certificate – is the best way to achieve
reliable information to use in comparisons. This type of program
is able to store all the history of calibrated weighing instruments,
including information for other measuring devices. It is also handy
for monitoring measuring systems. The most important aspect of a
calibration program is that it allows the user to select the calibration
method that corresponds to the required level of measuring tolerance,
and it displays the history of calibrations and in this way provides
the user with comprehensive information concerning measuring
capability.
calibration of weighing instruments
part 1
The purpose of calibration and complete confirmation
Calibration is a process where the user is able to confirm the correct
function of the weighing instrument based on selected information.
The user must define the limits for permitted deviation from a true
value and required measuring tolerance. If these values are exceeded,
an adjustment or maintenance is necessary.
Calibration itself, however, is a short-term process; the idea is that
the weighing instrument remains in good working condition until the
next calibration. For this reason, the user must determine all of the
external factors which may influence the proper functioning of the
weighing instrument. The factors in question may include the effect
of the environment where the weighing instrument is used and how
often the instrument needs to be cleaned, regular monitoring of the
zero point and the indication number with a constant mass.
Today, the function of weighing instruments, as well as many
other instruments, is based on microprocessors. They possess several
possibilities for adjusting parameters in measuring procedures.
Calibration should be carried out using settings based on the
parameters for normal use. It is very important that the users of the
weighing instruments, as well as calibration personnel, are familiar
with these parameters and use them as protocol. Since there are several
parameters in use, it is important to always have the manual for using
the weighing instrument easily available to the user.
Calibration itself, however,
is a short-term process;
the idea is that the
weighing instrument
remains in good working
condition until
the next calibration.
The content of the calibration certificate
Very often the calibration certificate is put on file as evidence of a
performed calibration to await the auditing of the quality system.
However, a quality system is usually concerned with the traceability
of measurements and the known measuring tolerance of the
measurements made. The calibration certificate of a single measuring
device is used as a tool for evaluating the process of measuring tolerance
and for displaying the traceability of the device in question.
Performing calibrations based on the measuring tolerance is better
than doing routine measuring. Therefore, the user must evaluate
the process of measuring tolerance and compare this value with the
required measuring tolerance of the process.
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calibration of weighing instruments
part 1
SUMMARY
Calibration (or verification) is a fundamental tool for
maintaining a measuring system. It also assists the user in
obtaining the required quality of measurements in a process.
The following must be taken into consideration:
• the type of procedure to be applied in confirming measuring
tolerance
• the interpretation of information while abiding by the
calibration certificate
• changing procedures based on received information
Quality calibration methods and data handling systems offer
state-of-the-art possibilities to any company.
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calibration of weighing instruments
part 1
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calibration of weighing instruments
part 11
Calibration of weighing instruments
Part 2
W
eighing is a common form of measurement in commerce,
industries and households. Weighing instruments are
often highly accurate, but users, i.e. their customers and/or
regulatory bodies, often need to know just how inaccurate a particular
scale may be. Originally, this information was obtained by classifying
and verifying the equipment for type approval. Subsequently, the
equipment was tested or calibrated on a regular basis.
Typical calibration procedures
Calibrating scales involves several different procedures depending
on national- and/or industry-specific guidelines or regulations, or on
the potential consequences of erroneous weighing results. One clear
and thorough guide is the EA-10/18, Guidelines on the Calibration
of Non-automatic Weighing Instruments, which was prepared by
the European Co-operation for Accreditation, and published by the
European Collaboration in Measurement and Standards (euromet).
Typical scale calibration involves weighing various standard weights
in three separate tests:
• repeatability test
• eccentricity test
• weighing test (test for errors of indication)
In the pharmaceutical industry in the United States, tests for
determining minimum weighing capability are also performed.
Weighing instruments are
often highly accurate, but
users, i.e. their customers
and/or regulatory bodies,
often need to know just
how inaccurate a particular
scale may be.
Repeated weighing measurements provide different indications
Usually, the object being weighed is placed on the load receptor
and the weighing result is read only once. If you weigh the object
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calibration of weighing instruments
part 11
repeatedly, you will notice slight, random variation in the indications.
The repeatability test involves weighing an object several times to
determine the repeatability of the scale used.
Center of gravity matters
Weighing instruments are
often highly accurate, but
users, i.e. their customers
and/or regulatory bodies,
often need to know just
how inaccurate a particular
scale may be.
The eccentricity test involves placing the object being weighed in the
middle of the load receptor as accurately as possible. This is sometimes
difficult due to the shape or construction of the object being weighed.
Typical calibration procedures include the eccentricity test. You can
determine how much the eccentricity of the load will affect the
indication on the scale by weighing the same weight at the corners of
the load receptor.
Test for errors in indication
The weighing test examines the error of the indication on the scale for
several predefined loads. This enables you to correct the errors and
definitions for non-linearity and hysteresis.
If the scale’s maximum load limit is extremely large, it may be
impractical to use standard weights for calibrating the entire range.
In such a case, suitable substitution mass is used instead. Substitution
mass should also be used if the construction of the scale does not allow
the use of standard weights.
A truck scale is unsuitable for weighing letters
The purpose of the minimum weight test is to determine the minimum
weight, which can be assuredly and accurately measured using the
scale in question. This condition is met if the measurement error is
less than 0.1% of the weight, with a probability of 99.73%.
Combined standard uncertainty of the error U(E)
Knowing the error of the scale indication at the point of each
calibration is not sufficient. You must also know how certain you can
be about the error found at each point of calibration. There are several
sources of uncertainty of the error, e.g.:
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calibration of weighing instruments
part 11
• The masses of the weights are only known with a certain uncertainty.
• Air convection causes extra force on the load receptor.
• Air buoyancy around the weights varies according to barometric
pressure, air temperature and humidity.
• A substitute load is used in calibrating the scale.
• Digital scale indications are rounded to the resolution in use.
• Analogous scales have limited readability.
• There are random variations in the indications as can be seen in the
Repeatability Test.
• The weights are not in the exact middle of the load receptor.
The values of uncertainty determined at each point of calibration are
expressed as standard uncertainties (coverage probability: 68.27%),
which correspond to one standard deviation of a normally distributed
variable. The combined standard uncertainty of the error at a certain
point of calibration has a coverage probability of 68.27% as well.
1.8 g
0.4 g
3.2 g
1.1 g
3.9 g
2.5 g
±u(E)
68.27%
U(E) = 2u(E)
95.45 %
U(E) = 3u(E)
99.73 %
4.6 g
Example: The calibration error
and its uncertainty at the
calibration point of 10 kg may
be expressed e.g. E = 2.5 g
and u(E) = ±0.7 g, which means
that the calculated error in the
indication is 2.5 g and the actual
error, with a coverage probability
of 68.27%, is between is between
1.8 g and 3.2 g.
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calibration of weighing instruments
part 11
Expanded uncertainty in calibration U(E)
The purpose of calibration
is to determine how
accurate a weighing
instrument is.
In practice, a coverage probability of 68.27% is insufficient. Normally,
it is extended to a level of 95.45% by multiplying it with the coverage
factor k = 2. If the distribution of the indicated error cannot be
considered normal, or the reliability of the standard uncertainty value
is insufficient, then a larger value should be used for the k-factor.
If you are able to use the k = 2 coverage factor, then the error and
its extended uncertainty at the point of calibration are E = 2.5 g and
U(E) = ±1.4 g. This means that the calculated error of the indication
is 2.5 g and the actual error, with a coverage probability of 95.45%, is
between 1.1 g and 3.9 g.
Uncertainty of a weighing result
The purpose of calibration is to determine how accurate a weighing
instrument is. As the above-mentioned case indicates, you know that
if you repeat the calibration several times, the indication of weighing
an object of 10 kilograms will be between 10.0011 kg and 10.0039 kg
95.45% of the time. However, the uncertainty of the results of later
routine weighings is usually larger. Typical reasons for this are:
• Routine weighing measurements involve random loads, while
calibration is made at certain calibration points.
• Routine weighing measurements are not repeated whereas indications
received through calibrations may be averages of repeated weighing
measurements.
• Finer resolution is often used in calibration.
• Loading/unloading cycles in calibration and routine weighing may
be different.
• A load may be situated eccentrically in routine weighing.
• Tare balancing device may be used in routine weighing.
• The temperature, barometric pressure and relative humidity of the
air may vary.
• The adjustment of the weighing instrument may have changed.
Standard and expanded uncertainties of weighing results are calculated
using technical data of the weighing instrument, its calibration results,
knowledge of its typical behaviour and knowledge of the conditions of
the location where the instrument is used. Defining the uncertainty
of weighing results is highly recommended, at least once, for all
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calibration of weighing instruments
part 11
typical applications and always for critical applications. Calculating
the uncertainty of weighing results assists you in deciding whether
or not the accuracy of the weighing instrument is sufficient and how
often it should be calibrated. However, determining the uncertainty
of weighing results is not part of calibration.
Calibrating and testing weighing instruments using CMX
CMX’s scale calibration enables you to uniquely configure calibration
and test each weighing instrument. Correspondingly, copying
configurations from one scale to another is easy. Error limits can be set
according to OIML or Handbook-44. Wide variation in user-specific
limits is also possible.
CMX calculates combined standard uncertainty and expanded
uncertainty at calibration of the weighing instrument. It allows you
to enter additional, user-defined uncertainty components in addition
to supported uncertainty components. CMX’s versatile calibration
certificate and possibility to define a user specific certificate assure
that you can fulfill requirements set for your calibration certificates.
CMX’s scale calibration
enables you to uniquely
configure calibration
and test each weighing
instrument.
141
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calibrating temperature instruments
Calibrating temperature instruments
T
he most commonly and most frequently measurable variable in
industry is temperature. Temperature greatly influences many
physical features of matter, and its influence on e.g. quality,
energy consumption and environmental emission is significant.
Temperature, being a state of equilibrium, makes it different from
other quantities. A temperature measurement consists of several
time constants and it is crucial to wait until thermal equilibrium is
reached before measuring. Metrology contains mathematic formulas
for calculating uncertainty. The polynoms are specified in ITS 90 table
(International Temperature Scale of 1990). For each measurement,
a model that includes all influencing factors must be created. Every
temperature measurement is different, which makes the temperature
calibration process slow and expensive.
While standards determine accuracy to which manufacturers
must comply, they nevertheless do not determine the permanency of
accuracy. Therefore, the user must be sure to verify the permanency of
accuracy. If temperature is a significant measurable variable from the
point of view of the process, it is necessary to calibrate the instrument
and the temperature sensor. It is important to keep in mind an old
saying: all meters, including sensors, show incorrectly, calibration will
prove by how much.
While standards
determine accuracy to
which manufacturers
must comply, they
nevertheless do
not determine the
permanency of accuracy.
Temperature sensors
The most commonly used sensors in the industry used for measuring
temperature are temperature sensors. They either convert temperature
into resistance (Resistance Temperature Detectors, RTD) or convert
temperature into low voltage (Thermocouples, T/C). RTD’s are based
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calibrating temperature instruments
on the fact that the resistance changes with temperature. Pt100 is a
common RTD type made of platinum and its resistance in 0 ˚C (32 ˚F)
is 100∧. Thermocouple consists of two different metal wires connected
together. If the connections (hot junction and cold junction) are
at different temperatures, a small temperature dependent voltage
difference/current can be detected. This means that the thermocouple
is not measuring the temperature, but the difference in temperature.
The most common T/C type is the K-type (NiCr/NiAl). Despite their
lower sensitivity (low Seebeck coefficient), the noble thermo-elements
S-, R- or B-type (PtRh/Pt, PtRh/Pt/Rh) are used especially in high
temperatures for better accuracy and stability.
The most important
criterion in the calibration
of temperature sensors
is how accurate the
sensors are at the same
temperature.
Temperature transmitters
The signal from the temperature sensor cannot be transmitted a
longer distance than the plant. Therefore, temperature transmitters
were developed to convert the sensor signal into a format that can
be transmitted easier. Most commonly, the transmitter converts the
signal from the temperature sensor into a standard ranging between 4
and 20 mA. Nowadays, transmitters with a digital output signal, such
as Fieldbus transmitters, are also being adopted, while the transmitter
converts the sensor signal, it also has an impact on the total accuracy,
and therefore the transmitter must be calibrated on regular basis.
A temperature transmitter can be calibrated using a temperature
calibrator.
Calibrating temperature instruments
To calibrate a temperature sensor, it must be inserted into a known
temperature. Sensors are calibrated either by using temperature
dry blocks for industrial field or liquid baths (laboratory). To make
comparisons, we compare the sensor to be calibrated and the reference
sensor. The most important criterion in the calibration of temperature
sensors is how accurate the sensors are at the same temperature.
The heat source may also have an internal temperature measurement
that can be used as reference, but to achieve better accuracy and
reliability, an external reference temperature sensor is recommended.
The uncertainty of calibration is not the same as the accuracy
of the device. Many factors influence the total uncertainty, and
performing calibration is not the least influencing factor. All heat
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calibrating temperature instruments
sources show measurement errors due to their mechanical design
and thermodynamic properties. These effects can be quantified
to determine the heat source’s contribution to the measurement
uncertainty. The major sources of measurement uncertainty are
axial homogeneity, radial homogeneity, loading effect, stability
and immersion depth. Guidelines for minimizing measurement
uncertainty should be applied according to Euramet/cg-13/v.01
(former EA-10/13).
Measurement uncertainty
Axial homogeneity
Axial homogeneity is the temperature distribution in the
measurement zone along the boring (axial temperature
distribution).
Radial homogeneity
Radial homogeneity can be explained as the difference in
temperature occurring between the borings.
The uncertainty of
calibration is not the same
as the accuracy of the
device.
Loading effect
When several sensors are placed in the borings of the heat
source, they will affect accuracy. This phenomenon is called
loading effect.
Stability
Stability means variation of the temperature in the measurement
zone over time when the system has reached equilibrium. Thirty
minutes is commonly used.
Immersion depth
To achieve a more stable calibration, the immersion depth for a
probe should be sufficient for the sensor being calibrated. Stem
conduction, heat flux along the length of the thermometer stem,
affects both the reference sensor and the unit being tested.
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calibrating temperature instruments
The calibration of instruments and sensors must be performed
periodically. The ISO quality control system presupposes the quality
control of calibration, the calibration of instruments effecting
production, regular calibration of sensors and traceable calibration
as well as calibration documentation. The level of performance a
calibration device needs to have depends on the accuracy requirements
determined by each company. However, the calibration device must
always be more accurate than the instrument or sensor being calibrated.
Calibration of instruments and sensors can be carried out either on
site or in a laboratory.
However, the calibration
device must always be
more accurate than the
instrument or sensor
being calibrated.
146
Integrated calibration solution – a smarter way to calibrate
temperature
Beamex has introduced a smarter, more efficient and accurate solution
for calibrating temperature. It is a complete solution for temperature
calibration with various products and services, such as a series of highquality dry blocks for field and laboratory use, smart reference probes
and temperature calibration laboratory services.
“The temperature products and services we are now introducing
form an integral part of the Beamex® Integrated Calibration Solution,
a complete calibration solution that enables faster, more accurate and
efficient management of all calibration assets and procedures”, says
Raimo Ahola, CEO of Beamex Group.
The Beamex® Integrated Calibration Solution concept is the
combination of calibrator, calibration software and PC for online
calibration. The instrument to be calibrated is connected to the
calibrator controlled by a computer, where the computer controls
the calibration event. The Beamex® FB and MB dry blocks are
part of the Beamex® Intergrated Calibration Solution. The dry
blocks communicate with the Beamex documenting multifunction
calibrators enabling fully automated temperature calibration and
documentation. The calibration results can then be uploaded from the
documenting calibrators to the Beamex® CMX Calibration Software.
The instrument’s calibration information is saved in the calibrator
and History Trend reports, both in numeric and in graphic form.
“This helps the client to follow the condition of the instrument, which
is useful in making decisions about purchasing new instruments,
determining service in advance and recalibration. With the CMX
Software, you can print out a calibration report as well as a traceable,
calibrating temperature instruments
accredited calibration certificate. Our integrated calibration solution
concept saves valuable time, eliminates any errors related to manual
entry and assures repeatable calibration procedures”, Mr Ahola adds.
The Beamex® Integrated
Calibration Solution
concept is the
combination of calibrator,
calibration software and
PC for online calibration.
147
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total uncertainty of temperature calibration
Calculating total uncertainty
of temperature calibration
with a dry block
T
his article will discuss the various uncertainty components related
to temperature calibration using a temperature dry-block. It will
also present how to calculate the total uncertainty of a calibration
performed with a dry block.
What is a temperature dry block?
A temperature dry block consists of a heatable and/or coolable metallic
block, controller, an internal control sensor and optional readout
for external reference sensor. This article will focus on models that
use interchangeable metallic multi-hole inserts. There are fast and
lightweight dry blocks for industrial field use as well as models that
deliver near bath-level stability in laboratory use. There are also some
work safety issues that favor dry blocks in preference to liquid baths.
For example, in temperatures above 200 °C liquids can produce
undesirable fumes or there may be fire safety issues. If a drop of water
gets into hot silicon oil, it could even cause a small steam explosion
which may splash hot oil on the user. Dry blocks are almost without
exception meant to be used dry. Heat transfer fluids or pastes are
sometimes used around or inside the insert, but they don’t necessarily
improve performance. They may actually even impede the dry block’s
performance and damage its internal components.
There are fast and
lightweight dry blocks for
industrial field use as well
as models that deliver
near bath-level stability in
laboratory use.
EURAMET
The EURAMET guideline (EURAMET /cg-13/v.01, July 2007
[previously EA-10/13]):
• The Euramet calibration guide defines a normative way to calibrate
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total uncertainty of temperature calibration
dry blocks. As most of the manufacturers nowadays publish their
product specifications including the main topics in the Euramet guide,
the products are easier to compare.
The Euramet calibration
guide defines a normative
way to calibrate dry
blocks.
• Main topics in the EURAMET guideline include:
– Display accuracy
– Axial uniformity
– Radial uniformity
– Loading
– Stability over time
– Hysteresis
– Sufficient immersion (15 x diameter)
– Stem loss for 6 mm or greater probes
– Probe clearance
(<= 0,5 mm at –80…660 °C)
(<= 1,0 mm at +660…1 300 °C)
Related uncertainty components
Uncertainty components that are related to temperature calibration are
relevant to all manufacturers’ dry blocks. Some manufacturers specify
these components and some do not.
It is possible to use a dry block with the block’s internal measurement
as the reference (true value), or to use an external reference temperature
probe inserted in the block as a reference measurement.
Internal measurement as reference
When using a dry block’s internal measurement as reference, the
following uncertainty components should be taken into account:
• D isplay accuracy (accuracy of the internal measurement)
It is important to remember that all of the thermometers based
on thermal contact measure their own temperature. With dry
blocks, the internal control sensor is typically located inside the
actual block, whereas the probes to be calibrated are immersed
in the insert. There is always thermal resistance between the
internal sensor and the probes inside the insert and other sources
of uncertainty need to be considered.
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total uncertainty of temperature calibration
MAIN PARTS OF THE DRY BLOCK
Stem conductance
Sensor to be
calibrated
Reference sensor
Axial uniformity
Internal sersor
Radial uniformity
Uncertainty components
that are related to
temperature calibration
are relevant to all
manufacturers’ dry
blocks.
• Axial uniformity
Axial uniformity refers to the variation in temperature along
the vertical length of the insert. The Euramet calibration guide
states, “dry wells should have a zone of sufficient temperature
homogeneity of at least 40 mm in length” at the bottom of the
insert. The purpose of this homogenous measurement zone is to
cover various sensor constructions. The thermocouple typically
has its “hot junction” close to the tip of the probe whereas the PRT
sensing element may be 30 to 50 mm long. With this in mind, a
homogenous zone of at least 60 mm is recommended.
• Radial uniformity
Radial uniformity refers to the variation in temperature between
the holes of the insert. Related uncertainty is caused, for example,
by the placement of the heaters, thermal properties of materials
and alignment of the insert holes. Non-symmetrical loading or
probes with significantly different thermal conductivity (for
example large diameter probes) may cause additional temperature
variation.
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total uncertainty of temperature calibration
• Loading effect
Every probe in the insert conducts heat either from or into the
insert. The more the load, the more the ambient temperature
will affect the measurements. Sufficient immersion depth and
dual zone control helps to reduce load-related uncertainties. The
loading effect is not visible in the control sensor indication and the
controller cannot completely compensate for this shift.
Stability describes how
well the temperature
remains the same during
a given time.
• Stability over time
– Stability describes how well the temperature remains the same
during a given time.
– The Euramet calibration guide defines stability as a temperature
variation over a 30-minute period, when the system has reached
equilibrium.
• Immersion
Sufficient immersion is important in any temperature measurement.
The Euramet calibration guide states that the immersion depth
should be at least 15 x the probe’s outer diameter. To minimize
the stem conduction error it’s recommended, as a rule of thumb,
to use immersion depth of 20 x the diameter, plus the length of
the sensing element. As the probe constructions vary greatly (sheet
material, wall thickness, lead wire thermal conductivity etc.), a test
for each individual probe type to be calibrated should be made.
If sufficient recommended immersion cannot be reached, then
the uncertainty caused by the insufficient immersion should be
estimated/ evaluated.
• Hysteresis
Hysteresis causes the internal sensor to be dependent on its previous
exposure. This means that the temperature of the dry block may
be a bit different depending on the direction from which the set
point is approached. The hysteresis is greatest at the mid-point and
is proportional to the temperature range.
The specifications for the above uncertainty components should be in
the block’s specifications. If some component has not been specified, it
should be estimated or evaluated.
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total uncertainty of temperature calibration
Using an external reference sensor as reference
Unlike using the dry block’s internal sensor as a reference, the external
reference sensor is inside the insert together with the probes to be
calibrated. Therefore, the external reference enables more accurate
measurement of the temperature of the probes to be calibrated. Using
an external reference sensor enables smaller total uncertainty of the
system. The internal sensor has to deal with quick temperature changes,
vibration and possible mechanical shocks so it has to be quite a robust
mechanically. Unfortunately, mechanical robustness is usually inversely
proportional to good performance: stability, hysteresis, etc.
The internal sensor is used just to adjust temperature close to the
desired calibration point and keep it stable. There are many advantages
to using a separate reference sensor. It helps to minimize calibration
uncertainty but also provides reliability in measurements. In the
case of using an external reference sensor, the following uncertainty
components should be taken into account:
• Axial uniformity
A xial uniformity-related uncertainty can be minimized by aligning
the centers of the sensing elements. In many cases, the user can
reduce the axial uniformity well below specification. In case the
probe to be calibrated is short and won’t reach the measurement
zone at the bottom of the insert, the reference probe can be drawn
out to match the immersion. Of course, the stem conductance has
to be taken into account. If the reference sensor and the sensor
to be calibrated are sufficiently similar in diameter and thermal
conductivity, the user may obtain good results.
Using an external
reference sensor
enables more accurate
measurement of the
temperature of the probes
to be calibrated.
• Radial uniformity
Radial uniformity is still present when using an external reference
probe and should be taken into account as specified.
• Loading effect
Since the internal sensor cannot completely compensate the loadrelated temperature shift inside the insert, the external reference
sensor is within the same calibration volume as the sensors to be
calibrated. The loading effect is usually much less significant with
an external reference sensor.
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total uncertainty of temperature calibration
• Stability over time
The external reference sensor can be used to measure the actual
temperature deviation inside the insert, and it may often be smaller
than the specification. It also helps the user to see when the unit
has truly stabilized. Dry blocks usually have a stability indicator,
but depending on, for instance, the different loads, there may still
be some difference between the block and the insert temperatures
when the indicator shows the unit has stabilized.
The external reference
sensor can be used
to measure the actual
temperature deviation
inside the insert and it
also helps the user to see
when the unit has truly
stabilized.
154
• External reference sensor
– The external reference sensor (PRT) is typically much more capable
of producing accurate measurements than the internal sensor.
However, using an external reference does not automatically mean
better results. All of the previously mentioned uncertainty factors
need to be carefully considered.
– Uncertainty related to the reference probe components includes the
probe’s calibration uncertainty, drift, hysteresis, stem conduction,
and the readout device’s uncertainty.
– Of course, the external reference sensor needs a unit that measures
the sensor. It can be the block or an external device.
total uncertainty of temperature calibration
CALCULATION EXAMPLES
■ Here are two examples
of total uncertainty
calculations. One is
done using the internal
temperature measurement
and the other with a
reference probe. In both
cases the MB155R is used
as the dry block.
The temperature in both
examples is 0 °C.
Due to the rectangular
probability distribution of
the specifications, they
are divided by the square
root of three to get the
Standard Uncertainty. The
standard uncertainties
are combined as the root
sum of the squares. Finally
the combined uncertainty
has been multiplied by
two to get the expanded
uncertainty.
As can be seen in the
examples the total
expanded uncertainty
using the internal reference
sensor is 135 mK
(0.135 °C). When using
an external reference
sensor the total expanded
uncertainty is 34 mK
(0.034 °C).
The various uncertainty
components used in the
examples can be found in
the specifications in the
product brochures.
MB155R with internal measurement @0 °C
Component
Specification (°C)
Standard Uncertainty (°C)
Display Accuracy
0.10
0.058
Hysteresis
0.025
0.014
Axial Uniformity
0.02
0.012
Radial Uniformity
0.01
0.006
Stability
0.005
0.003
Loading Effect
0.05
0.029
Combined Uncertainty:
0.067
Expanded Uncertainty:
0.135
MB155R with external measurement @0 °C
Component
Specification (°C)
Standard Uncertainty (°C)
Axial Uniformity
0.02
0.012
Radial Uniformity
0.01
0.006
Stability
0.005
0.003
Loading Effect
0.005
0.003
0.006
0.003
Ref sensor measurement
Combined Uncertainty:
0.014
Expanded Uncertainty:
0.028
Reference Sensor (Beamex RPRT-420)
Component
Specification (°C)
Standard Uncertainty (°C)
Short-term repeatability
0.007
0.004
Drift
0.007
0.004
Hysteresis
0.01
0.006
0.01
0.006
Calibration uncertainty
Combined Uncertainty:
0.010
Expanded Uncertainty:
0.020
Combined uncertainty:
0.017
Expanded Uncertainty:
0.034
MB155R and RPRT-420
All specifications have a rectangular probability distribution.
That is why they are divided by the square root of three to get Standard Uncertainty.
155
fieldbus transmitters must also be calibrated
Fieldbus transmitters
must also be calibrated
F
ieldbus is becoming more and more common in today’s
instrumentation. But what is fieldbus and how does it differ from
conventional instrumentation? Fieldbus transmitters must be
calibrated as well, but how can it be done?
Conventional transmitters can deliver only one simultaneous
parameter, one way. Each transmitter needs a dedicated pair of cables,
and I/O subsystems are required to convert the analog mA signal to a
digital format for a control system.
Fieldbus transmitters are able to deliver a huge amount of
information via the quick two-way bus. Several transmitters
can be connected to the same pair of wires. Conventional I/O
systems are no longer needed because segment controllers connect the
instrument segments to the quicker, higher-level fieldbus backbone.
Being an open standard, instruments from any manufacturer can
be connected to the same fieldbus as plug-and-play.
Fieldbus transmitters
must be calibrated as
well, but how can it be
done?
History of fieldbus
Back in the 1940s, instrumentation utilized mainly pneumatic signals
to transfer information from transmitters. During the 1960s, the mA
signal was introduced, making things much easier. In the 1970s,
computerized control systems began to make their arrival. The first
digital, smart transmitter was introduced in the 1980s, using first
proprietary protocols. The first fieldbus was introduced in 1988, and
throughout the 1990s a number of various fieldbuses were developed.
During the 1990s, manufacturers battled to see whose fieldbus
would be the one most commonly used. A standard was finally set
in the year 2000 when the IEC61158 standard was approved. The
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fieldbus transmitters must also be calibrated
Foundation Fieldbus H1 and the Profibus PA, both used in process
instrumentation, were chosen as standards.
For the most part, one can say that the Foundation Fieldbus is
dominating the North American markets and the Profibus is the
market leader in Europe. Other areas are more divided. There are also
certain applications that prefer certain fieldbus installations despite
the geographical location.
Future of fieldbus
The Foundation Fieldbus
and Profibus have begun
to clearly dominate the
fieldbus market.
Currently, a large number of fieldbus installations already exist and
the number is increasing at a huge rate. A large portion of new projects
is currently being carried out using fieldbus. Critical applications and
hazardous areas have also begun to adopt fieldbus.
The Foundation Fieldbus and Profibus have begun to clearly
dominate the fieldbus markets. Both Foundation Fieldbus and Profibus
have reached such a large market share that both buses will most likely
remain also in the future. The development of new fieldbuses has
slowed down and it is unlikely that new fieldbus standards will appear
in the near future to challenge the position of Foundation Fieldbus
or Profibus.
Recent co-operation between Foundation Fieldbus and Profibus
suppliers will further strengthen the position of these two standards.
Fieldbus benefits for industry
Obviously process plants would not start utilizing fieldbus, if it
would not offer them benefits compared to alternative systems.
One important reason is the better return on investment. Although
fieldbus hardware may cost the same as conventional, or even a little
bit more, the total installation costs for a fieldbus factory is far less
than conventional. This is caused by many reasons, such as reduction
in field wiring, lower installation labour cost, less planning/drawing
costs, and no need for conventional I/O subsystems.
Another big advantage is the on-line self-diagnostics that helps in
predictive maintenance and eventually reduces the downtime, offering
maintenance savings. Remote configuration also helps to support
reduced downtime. The improved system performance is important
criteria for some plants. There are also other advantages compared to
conventional instrumentation.
158
fieldbus transmitters must also be calibrated
Fieldbus transmitters must also be calibrated
The main difference between a fieldbus transmitter for pressure or
temperature and conventional or HART transmitters is that the output
signal is a fully digital fieldbus signal.
The other parts of a fieldbus transmitter are mainly comparable
to conventional or HART transmitters. Changing the output
signal does not change the need for periodic calibration. Although
modern fieldbus transmitters have been improved compared to older
transmitter models, it does not eliminate the need for calibration.
There are also many other reasons, such as quality systems and
regulations, that make the periodic calibrations compulsory.
Calibrating fieldbus transmitters
The word “calibration” is often misused in the fieldbus terminology
when comparing it to the meaning of the word in metrology. In fieldbus
terminology, “calibration” is often used to mean the configuration of
a transmitter. In terminology pertaining to metrology, “calibration”
means that you compare the transmitter to a traceable measurement
standard and document the results.
So it is not possible to calibrate a fieldbus transmitter using only
a configurator or configuration software. Also, it is not possible to
calibrate a fieldbus transmitter remotely.
Fieldbus transmitters are calibrated in very much the same way as
conventional transmitters – you need to place a physical input into
the transmitter and simultaneously read the transmitter output to see
that it is measuring correctly. The input is measured with a traceable
calibrator, but you also need to have a way to read the output of the
fieldbus transmitter. Reading the digital output is not always an easy
thing to do.
When fieldbus is up and running, you can have one person in the
field to provide and measure the transmitter input while another
person is in the control room reading the output. Naturally these two
people need to communicate with each other in order to perform and
document the calibration.
While your fieldbus and process automation systems are idle, you
need to find other ways to read the transmitter’s output. In some cases
you can use a portable fieldbus communicator or a laptop computer
with dedicated software and hardware.
Although fieldbus
hardware may cost the
same as conventional,
or even a little bit more,
the total installation costs
for a fieldbus factory is
far less than conventional.
159
fieldbus transmitters must also be calibrated
Fieldbus instruments are increasing in popularity and calibration
can in many cases be cumbersome, time-consuming and may require
an abundance of resources.
The Beamex® MC6 will help to overcome these challenges by
combining a full field communicator and an extremely accurate
multifunctional process calibrator. The Beamex® MC6 can be used
as a communicator for the configuration as well as a calibrator for the
calibration of smart instruments with the supported protocols. There
is no need for an additional communicator. The calibration results can
be automatically stored into the memory of the MC6 or uploaded to
calibration software.
The Beamex® MC6
can be used as a
communicator for the
configuration as well
as a calibrator for the
calibration of smart
instruments with the
supported protocols.
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configuring and calibrating smart instruments
Configuring and calibrating
smart instruments
S
o called “smart” instruments are ever more popular in the process
industry. The vast majority of delivered instruments today are
smart instruments. These new smart instruments bring new
challenges to the calibration and configuration processes. But what
are these smart instruments and what is the best way to configure and
calibrate them?
Beamex has recently introduced a new revolutionary tool, the
Beamex® MC6 –Advanced Field Communicator and Calibrator, that
will help to overcome these challenges.
A modern smart
transmitter typically
outperforms an older type
of conventional transmitter
regarding measurement
accuracy and stability.
What is a “smart” transmitter?
A process transmitter is a device that senses a physical parameter
(pressure, temperature, etc.) and generates an output signal
proportional to the measured input. The term “smart” is more of a
marketing term than a technical definition. There is no standardized
technical definition for what smart really means in practice.
Generally, in order for a transmitter to be called smart, it will utilize
a microprocessor and should also have a digital communication
protocol that can be used for reading the transmitter’s measurement
values and for configuring various settings in the transmitter. A
microprocessorbased smart transmitter has a memory that can
perform calculations, produce diagnostics, etc. Furthermore, a modern
smart transmitter typically outperforms an older type of conventional
transmitter regarding measurement accuracy and stability.
In any case, for the engineers who need to configure and calibrate
the transmitter, the digital communication protocol is the biggest
difference compared to conventional transmitters. Engineers can
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configuring and calibrating smart instruments
no longer simply measure the output analog signal, but they need to
have the possibility to communicate with the transmitter and read the
digital signal. That brings a whole new challenge - how can the digital
output be read?
Thinking of the opposite of a smart transmitter, i.e. a non-smart
transmitter, would be a transmitter with a purely analog (or even
pneumatic) output signal.
Smart transmitter protocols
It is crucial to remember
that although a
communicator can be
used for configuration, it is
not a reference standard
and therefore cannot be
used for metrological
calibration.
There are various digital protocols that exist among transmitters
considered smart. Some are proprietary protocols of a certain
manufacturer, but these seem to be fading out in popularity and favor
is being given to protocols based on open standards because of the
interoperability that they enable.
Most of the protocols are based on open standards. The most
common transmitter protocol today is the HART (Highway
Addressable Remote Transducer) protocol. A HART transmitter
contains both a conventional analog mA signal and a digital signal
superimposed on top of the analog signal. Since it also has the analog
signal, it is compatible with conventional installations. Recently the
HART protocol seems to be getting more boosts from the newest
WirelessHART protocol.
The fieldbuses, such as Foundation Fieldbus and Profibus, contain
only a digital output, no analog signal. Foundation Fieldbus and
Profibus are gaining a larger foothold on the process transmitter
markets.
This article will discuss “smart” transmitters, including HART,
WirelessHART, Foundation Fieldbus and Profibus PA protocols.
Configuration
One important feature of a smart transmitter is that it can be
configured via the digital protocol. Configuration of a smart
transmitter refers to the setting of the transmitter parameters. These
parameters may include engineering unit, sensor type, etc. The
configuration needs to be done via the communication protocol. So
in order to do the configuration, you will need to use some form of
configuration device, typically also called a communicator, to support
the selected protocol.
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configuring and calibrating smart instruments
It is crucial to remember that although a communicator can be used
for configuration, it is not a reference standard and therefore cannot
be used for metrological calibration. Configuring the parameters of a
smart transmitter with a communicator is not in itself a metrological
calibration (although it may be part of an adjustment/trim task) and
it does not assure accuracy. For a real metrological calibration, by
definition a traceable reference standard (calibrator) is always needed.
Calibration of a smart transmitter
According to international standards, calibration is a comparison of the
device under test against a traceable reference instrument (calibrator)
and documenting the comparison. Although the calibration formally
does not include any adjustments, potential adjustments are often
included when the calibration process is performed. If the calibration
is done with a documenting calibrator, it will automatically document
the calibration results.
To calibrate a conventional, analog transmitter, you can generate
or measure the transmitter input and at the same time measure the
transmitter output. In this case calibration is quite easy and straight
forward; you need a dual-function calibrator able to process transmitter
input and output at the same time, or alternatively two separate singlefunction calibrators.
But how can a smart transmitter, with output being a digital protocol
signal, be calibrated? Obviously the transmitter input still needs to be
generated/measured the same way as with a conventional transmitter,
i.e. by using a calibrator. However, to see what the transmitter output
is, you will need some device or software able to read and interpret the
digital protocol. The calibration may, therefore, be a very challenging
task; several types of devices may be needed and several people to
do the job. Sometimes it is very difficult or even impossible to find
a suitable device, especially a mobile one, which can read the digital
output.
Wired HART (as opposed to WirelessHART) is a hybrid protocol
that includes digital communication superimposed on a conventional
analog 4–20mA output signal. The 4–20mA output signal of a wired
HART transmitter is calibrated the same way as a conventional
transmitter. However, to do any configuration or trimming, or to
read the digital output signal (if it is used), a HART communicator
is needed.
The transmitter input
needs to be generated/
measured the same way
as with a conventional
transmitter, i.e. by using a
calibrator, but in order to
see what the transmitter
output is, a device or
software able to read
and interpret the digital
protocol is needed.
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configuring and calibrating smart instruments
The solution
With the Beamex® MC6,
the smart transmitter’s
input can be generated/
measured at the same
time as reading the digital
output.
The new Beamex ® MC6 is a device combining a full field
communicator and an extremely accurate multifunctional process
calibrator. With the Beamex® MC6, the smart transmitter’s input can
be generated/ measured at the same time as reading the digital output.
The results can be automatically stored into the memory of the MC6
or uploaded to calibration software.
When it comes to configuration of the smart transmitters, the
MC6 includes a full field communicator for HART, WirelessHART,
Foundation Fieldbus H1 and Profibus PA protocols. All required
electronics are built-in, including power supply and required
impedances for the protocols.
The Beamex® MC6 can be used both as a communicator for
the configuration and as a calibrator for the calibration of smart
instruments with the supported protocols. The MC6 supports all of the
protocol commands according to the transmitter’s device description
file. Any additional communicator is therefore not needed.
There are some other “smart” process calibrators on the market with
limited support for different protocols, typically only for one protocol
(mostly HART) and offering very limited support. In practice, a
separate communicator is needed in any case.
About Beamex® MC6
Beamex® MC6 is an advanced, high-accuracy field calibrator
and communicator. It offers calibration capabilities for pressure,
temperature and various electrical signals. The MC6 also contains
a full fieldbus communicator for HART, Foundation Fieldbus and
Profibus PA instruments.
The usability and ease-of-use are among the main features of the
MC6. It has a large 5.7" color touch-screen with a multilingual user
interface. The robust IP65-rated dustand water-proof casing, ergonomic
design and light weight make it an ideal measurement device for field
use in various industries, such as the pharmaceutical, energy, oil
and gas, food and beverage, service as well as the petrochemical and
chemical industries.
The MC6 is one device with five different operational modes,
which means that it is fast and easy to use, and you can carry less
equipment in the field. The operation modes are: meter, calibrator,
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configuring and calibrating smart instruments
documenting calibrator, data logger and Fieldbus communicator. In
addition, the MC6 communicates with Beamex® CMX Calibration
Software, enabling fully automated and paperless calibration and
documentation.
In conclusion, the MC6 is more than a calibrator.
Why calibrate?
A modern transmitter is advertised as being smart and extremely
accurate and sometimes sales people tell you they don’t need
to be calibrated at all because they are so “smart”. So why
would you calibrate them? First of all, the output protocol of a
transmitter does not change the fundamental need for calibration.
There are numerous reasons to calibrate instruments initially and
periodically. A short summary of the main reasons include;
The MC6 also contains a
full fieldbus communicator
for HART, Foundation
Fieldbus and Profibus PA
instruments.
• Even the best instruments and sensors drift over time,
especially when used in demanding process conditions.
• Regulatory requirements, such as quality systems, safety
systems, environmental systems, standards, etc.
• Economical reasons – any measurement having direct
economical effect.
• Safety reasons- employee safety as well as customer/patient
safety.
• To achieve high and consistent product quality
and to optimize processes.
• Environmental reasons.
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calibration in hazardous environments
Calibration in
hazardous environments
S
triking a match in an environment that contains combustible
gas is nothing short of dangerous – personal injury and property
damage are likely consequences. Improperly calibrating an
instrument in this hazardous environment can be almost as dangerous.
The materials and fluids used in some processes can be hazardous in
the sense that they can ignite or explode. For example, hydrocarbons
in mines, oil refineries, and chemical plants are flammable and are
typically contained within vessels and pipes. If this were truly the case,
an external flame would not ignite the hydrocarbons. However, in
many locations, leaks, abnormal conditions, and fluid accumulation
may allow hydrocarbons to be present such that the flame could ignite
the hydrocarbons with disastrous results.
Hydrocarbons and other flammable fluids are not limited to the
petroleum and chemical industries. For example, combustible fuels,
such as natural gas, are used in all industries, including agriculture,
food, pharmaceuticals, power generation, pulp/paper, water/
wastewater, universities, retail, and in the home.
In addition, many materials and fluids used in seemingly “safe”
industries are themselves flammable. Even seemingly safe water
treatment systems use combustible materials such as chlorine in their
processes. This means that certain areas of a water treatment plant
may well be considered hazardous. Similarly, certain areas of food
plants, such as reactors that hydrogenate oils, may pose hazards as
well. Therefore, it is important for plants to examine their processes
and identify hazardous locations so that the proper instruments are
Many materials and fluids
used in seemingly “safe”
industries are themselves
flammable.
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calibration in hazardous environments
selected, installed, and maintained in accordance with practices that
are appropriate for the hazard.
Equipment requirements in hazardous locations
Protection requirements for hazardous locations vary according to the
type of material present, frequency of the hazard, and the protection
concept applied.
The intensity with which various vapors can combust is generally
different. Groupings (IEC 60079-10) in order of decreasing ignition
energy (with an example of a gas in the group) are:
Intrinsic Safety (IS)
is the most common
protection concept
applied to calibrators
used in hazardous
locations.
Group IIC
Group IIB+H2
Group IIB
Group IIA
Acetylene
Hydrogen
Ethylene
Propane
The hazardous area classifications (IEC 60079-10) in order of
decreasing frequency are:
Zone 0 Flammable material present continuously
Zone 1 Flammable material present intermittently
Zone 2
Flammable material present abnormally
Intrinsic Safety (IS) is the most common protection concept applied
to calibrators that are used in hazardous locations. In general, the IS
concept is to design the calibrator such that it limits the amount of
energy available such that it cannot ignite a combustible gas mixture.
Adding the applicability of IS designs to various hazards in the
previous table yields:
Zone 0 ia Flammable material present continuously
Zone 1 ia, ib Flammable material present intermittently
Zone 2 ia, ib Flammable material present abnormally
In addition, a hot surface temperature on a device can cause ignition.
Temperature classes limit the maximum surface temperature between
450˚C (T1) and 85˚C (T6).
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calibration in hazardous environments
Beamex calibrators for hazardous locations are designed and certified
for Ex ia IIC T4 hazards per the ATEX Directive and are applicable to
all vapor hazards where a temperature class of 135˚C in a 50˚C ambient
is acceptable. As such, they can be used for the overwhelming majority
of applications where a vapor hazard is present.
Calibration solutions for hazardous locations
Instruments designed to measure flow, level, pressure, temperature,
and other variables designed in hazardous locations are generally used
to monitor and control the process. In some applications, it is practical
to remove these instruments and calibrate them on the workshop with
a calibration test bench. This is usually not the case, which means that
many instruments are calibrated in the field. Fortunately, there are
calibrators that are specifically designed to operate safely in rugged
environments and hazardous locations.
The Beamex multifunction IS-calibrators are portable and
intrinsically safe and have modules that can accommodate wide ranges
and many types of pressure, RTD, thermocouple, voltage, current,
pulse, and frequency measurements.
The Beamex modular calibration system is a test bench and
calibration system for workshops and laboratories that incorporates
the functionality of the MC5 multifunction calibrator and can
measure/generate additional parameters such as precision pressures.
The ergonomic design and modular construction allow the user to
select the necessary functions in a cost-effective manner.
The Beamex® CMX software integrates calibration management by
allowing efficient planning and scheduling of calibration work. It not
only alerts you when to calibrate, but also automatically takes data,
creates documentation, adheres to GMP regulations (21 CFR 11), and
tracks calibration history. This software generally makes calibration
work faster and easier and is designed to integrate into management
systems such as SAP and Maximo.
The Beamex® CMX
software integrates
calibration management
by allowing efficient
planning and scheduling
of calibration work.
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calibration in hazardous environments
A few points to remember
• Improper actions in hazardous locations can result in property
damage and bodily injury.
• Hazardous locations can exist in virtually all industries, stores, and
in the home.
• Instruments should be specified, installed, operated, and maintained
in accordance with requirements for the hazardous location.
Hazardous locations
can exist in virtually all
industries, stores,
and in the home.
172
• Portable Beamex calibrators for hazardous locations are designed to
be used in virtually all vapor hazards.
calibration in hazardous environments
173
the safest way to calibrate fieldbus instruments
The safest way to calibrate
fieldbus instruments
F
ieldbus transmitters must also be calibrated just like conventional
instruments. There are also industrial environments where the
calibration of fieldbus instruments should not only be made
accurately and efficiently, but also safely. When safety becomes a top
priority issue in calibration, intrinsically safe fieldbus calibrators enter
into the picture.
By definition, intrinsic safety (IS) is a protection technique for
safely operating electronic equipment in explosive environments.
The concept has been developed for safely operating process control
instrumentation in hazardous areas. The idea behind intrinsic safety
is to make sure that the available electrical and thermal energy in a
system is always low enough that ignition of the hazardous atmosphere
cannot occur. A hazardous atmosphere is an area that contains
elements that may cause an explosion: source of ignition, a flammable
substance and oxygen.
An intrinsically safe calibrator is therefore designed to be incapable
of causing ignition in the surrounding environment with flammable
materials, such as gases, mists, vapors or combustible dust. Intrinsically
safe calibrators are also often referred to being “Ex calibrators”,
“calibrators for Ex Areas”, or “IS calibrators”. An Ex Area also refers
to an explosive environment and an Ex calibrator is a device designed
for use in the type of environment in question.
Hazardous area
classifications in IEC/
European countries are:
Zone 0: an explosive gas
& air mixture is continuously
present or present for a long
time.
Zone 1: an explosive gas &
air mixture is likely to occur
in normal operation.
Zone 2: an explosive gas
& air mixture is not likely to
occur in normal operation,
and if it occurs it will exist
only for a short time.
Where is intrinsically safe calibration required?
Many industries require intrinsically safe calibration equipment.
Intrinsically safe calibrators are designed for potentially explosive
environments, such as oil refineries, rigs and processing plants, gas
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the safest way to calibrate fieldbus instruments
pipelines and distribution centres, petrochemical and chemical plants,
as well as pharmaceutical plants. Basically, any potentially explosive
industrial environment can benefit from using intrinsically safe
calibrators.
What are the benefits of using intrinsically safe calibrators?
There are clear benefits in using intrinsically safe calibration
equipment. First of all, it is the safest possible technique. Secondly,
the calibrators provide performance and functionality.
Basically, any potentially
explosive industrial
environment can benefit
from using intrinsically
safe calibrators.
Safest possible technique
Intrinsically safe calibrators are safe for employees, as they
can be safely used in environments where the risk of an
explosion exists. In addition, intrinsically safe calibrators
are the only technique permitted for Zone 0 environments
(explosive gas and air mixture is continuously present or
present for a long time).
Performance and functionality
Multifunctional intrinsically safe calibrators provide
the functionality and performance of regular industrial
calibration devices, but in a safe way. They can be used
for calibration of pressure, temperature and electrical
signals. A documenting intrinsically safe calibrator, such
as the Beamex® MC5- IS, provides additional efficiency
improvements with its seamless communication with
calibration software. This eliminates the need of manual
recording of calibration data and improves the quality and
productivity of the entire calibration process.
Are intrinsically safe calibrators technically different from regular
industrial calibrators?
Intrinsically safe calibrators are different from other industrial
calibrators in both design and technical features. In view of safety,
there are also some guidelines and constraints for how to use them in
hazardous areas. Every intrinsically safe calibrator is delivered with a
product safety note, which should be read carefully before using the
device. The product safety note lists all the “do’s and don’ts” for safe
calibration.
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the safest way to calibrate fieldbus instruments
The differences in design and technical features were made with one
purpose in mind—to ensure that the device is safe to use and is unable
to cause an ignition. The surface of the device is made of conductive
material. The battery of an intrinsically safe calibrator is usually slower
to charge and it discharges quicker. Many times intrinsically safe
equipment operate only with dry batteries, but the Beamex intrinsically
safe calibrators operate with chargeable batteries. When charging the
battery, it must be done in a non-Ex area. External pressure modules
can be used with IS-calibrators, but they must also be intrinsically
safe. There are also usually small differences with electrical ranges
compared to regular industrial calibrators (e.g. maximum is lower).
Making a calibrator safe and unable to cause ignition – typical
technical differences:
• Surface made of conductive material
• Constraints in using the device (listed in Product Safety Note)
• Small differences with electrical ranges (e.g. maximum is lower)
• Battery slower to charge, quicker to discharge
• Battery must be charged in a non-Ex area
• When using external pressure modules, they must be IS-versions
The differences in design
and technical features
were made with one
purpose in mind – to
ensure that the device is
safe to use and is unable
to cause an ignition.
What are ATEX and IECEx?
ATEX (“ATmosphères EXplosibles”, explosive atmospheres in French)
is a standard set in the European Union for explosion protection in the
industry. ATEX 95 equipment directive 94/9/EC concerns equipment
intended for use in potentially explosive areas. Companies in the
EU where the risk of explosion is evident must also use the ATEX
guidelines for protecting the employees. In addition, the ATEX rules
are obligatory for electronic and electrical equipment that will be used
in potentially explosive atmospheres sold in the EU as of July 1, 2003.
IEC (International Electrotechnical Commission) is a nonprofit
international standards organization that prepares and publishes
international standards for electrical technologies. The IEC TC/31
technical committee deals with the standards related to equipment for
explosive atmospheres. IECEx is an international scheme for certifying
procedures for equipment designed for use in explosive atmospheres.
The objective of the IECEx Scheme is to facilitate international trade
in equipment and services for use in explosive atmospheres, while
maintaining the required level of safety.
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the safest way to calibrate fieldbus instruments
As Beamex® MC5-IS Intrinsically Safe Multifunction Calibrator is
certified according to ATEX and the IECEx Scheme, it ensures the
calibrator is fit for its intended purpose and that sufficient information
is supplied with it to ensure that it can be used safely.
Is service different for intrinsically safe calibrators?
The most important thing
to remember is that an
intrinsically safe calibrator
must maintain its intrinsic
safety after the service or
repair.
178
There are certain aspects that need special attention when doing
service or repair on an intrinsically safe calibrator. The most important
thing to remember is that an intrinsically safe calibrator must maintain
its intrinsic safety after the service or repair. The best way to do this
is to send it to the manufacturer or to an authorized service company
for repair. Recalibration can be done by calibration laboratories (still
preferably with ISO/IEC 17025 accreditation).
Safe fieldbus calibration with the Beamex® MC5-IS Intrinsically
Safe Multifunction Calibrator
The Beamex® MC5-IS Intrinsically Safe Multifunction Calibrator
is a high accuracy, all-in-one calibrator for extreme environments.
Being an all-in-one calibrator, the MC5-IS replaces many individual
measurement devices and calibrators. The MC5-IS is also ATEX
and IECEx certified. The MC5-IS has calibration capabilities
for pressure, temperature, electrical and frequency signals. It is
a documenting calibrator, which means that it communicates
seamlessly with calibration software. Using documenting calibrators
with calibration software can remarkably improve the efficiency and
quality of the entire calibration process. The MC5-IS also has HART
communication. The MC5-IS also has HART communication. The
MC5-IS can also be used for calibrating Foundation Fieldbus H1 or
Profibus PA transmitters.
appendix: calibration terminology a to z
1
Calibration terminology
A to Z
1
T
his glossary is a quick reference to the meaning of common
terms. It is a supplement to the VIM, GUM, NCSL Glossary,
and the information in the other references listed at the end.
In technical, scientific and engineering work (such as metrology)
it is important to correctly use words that have a technical meaning.
Definitions of these words are in relevant national, international
and industry standards; journals; and other publications, as well as
publications of relevant technical and professional organizations.
Those documents give the intended meaning of the word, so everyone
in the business knows what it is. In technical work, only the technical
definitions should be used.
Many of these definitions are adapted from the references. In some
cases several may be merged to better clarify the meaning or adapt
the wording to common metrology usage. The technical definitions
may be different from the definitions published in common grammar
dictionaries. However, the purpose of common dictionaries is to record
the ways that people actually use words, not to standardize the way
the words should be used. If a word is defined in a technical standard, its
definition from a common grammar dictionary should never be used in work
where the technical standard can apply.
______________
1. Bucher, Jay L. 2004. The Metrology Handbook. Milwaukee: ASQ Quality Press.
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appendix: calibration terminology a to z
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Terms that are not in this glossary may be found in one of these
primary references:
1. ISO. 1993. International vocabulary of basic and general terms in
metrology (called the VIM); BIPM, IEC, IFCC, ISO, IUPAC,
IUPAP, and OIML. Geneva: ISO.
2. ANSI/NCSL. 1997. ANSI/NCSL Z540-2-1997, U. S. Guide to the
expression of uncertainty in measurement (called the GUM). Boulder,
CO: NCSL International.
3. NCSL. 1999. NCSL Glossary of metrology-related terms. 2nd ed.
Boulder, CO: NCSL International.
Some terms may be listed in this glossary in order to expand on
the definition, but should be considered an addition to the references
listed above, not a replacement of them. (It is assumed that a calibration
or metrology activity owns copies of these as part of its basic reference
material.)
Glossary
Accreditation (of a laboratory) – Formal recognition by an accreditation
body that a calibration or testing laboratory is able to competently
perform the calibrations or tests listed in the accreditation
scope document. Accreditation includes evaluation of both the
quality management system and the competence to perform the
measurements listed in the scope.
Accreditation body – An organization that conducts laboratory
accreditation evaluations in conformance to ISO Guide 58.
Accreditation certificate – Document issued by an accreditation
body to a laboratory that has met the conditions and criteria for
accreditation. The certificate, with the documented measurement
parameters and their best uncertainties, serves as proof of accredited
status for the time period listed. An accreditation certificate
without the documented parameters is incomplete.
Accreditation criteria – Set of requirements used by an accrediting
body that a laboratory must meet in order to be accredited.
Accuracy (of a measurement) – Accuracy is a qualitative indication of
how closely the result of a measurement agrees with the true value
of the parameter being measured. (VIM, 3.5) Because the true
value is always unknown, accuracy of a measurement is always
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1
an estimate. An accuracy statement by itself has no meaning
other than as an indicator of quality. It has quantitative value
only when accompanied by information about the uncertainty
of the measuring system. Contrast with: accuracy (of a measuring
instrument)
Accuracy (of a measuring instrument) – Accuracy is a qualitative
indication of the ability of a measuring instrument to give
responses close to the true value of the parameter being measured.
(VIM, 5.18) Accuracy is a design specification and may be verified
during calibration. Contrast with: accuracy (of a measurement)
Application – Software installed on a defined platform/hardware
providing specific functionality
Assessment – Examination typically performed on-site of a testing or
calibration laboratory to evaluate its conformance to conditions
and criteria for accreditation.
Bespoke/Customized computerised system – A computerised system
individually designed to suit a specific business process
Best measurement capability – For an accredited laboratory, the best
measurement capability for a particular quantity is “the smallest
uncertainty of measurement a laboratory can achieve within its
scope of accreditation when performing more or less routine
calibrations of nearly ideal measurement standards intended to
define, realize, conserve, or reproduce a unit of that quantity or
one or more of its values; or when performing more-or-less routine
calibrations of nearly ideal measuring instruments designed for the
measurement of that quantity.” (EA-4/02) The best measurement
capability is based on evaluations of actual measurements
using generally accepted methods of evaluating measurement
uncertainty.
Bias – Bias is the known systematic error of a measuring instrument.
(VIM, 5.25) The value and direction of the bias is determined by
calibration and/or gage R&R studies. Adding a correction, which
is always the negative of the bias, compensates for the bias. See also:
correction, systematic error
Calibration – (1). (See VIM 6.11 and NCSL pages 4–5 for primary
and secondary definitions.) Calibration is a term that has many
different – but similar – definitions. It is the process of verifying
the capability and performance of an item of measuring and test
equipment by comparison to traceable measurement standards.
Calibration is performed with the item being calibrated in
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1
its normal operating configuration – as the normal operator
would use it. The calibration process uses traceable external
stimuli, measurement standards, or artifacts as needed to verify
the performance. Calibration provides assurance that the
instrument is capable of making measurements to its performance
specification when it is correctly used. The result of a calibration is
a determination of the performance quality of the instrument with
respect to the desired specifications. This may be in the form of
a pass/fail decision, determining or assigning one or more values,
or the determination of one or more corrections. The calibration
process consists of comparing an IM&TE unit with specified
tolerances, but of unverified accuracy, to a measurement system
or device of specified capability and known uncertainty in order
to detect, report, or minimize by adjustment any deviations from
the tolerance limits or any other variation in the accuracy of the
instrument being compared. Calibration is performed according
to a specified documented calibration procedure, under a set of
specified and controlled measurement conditions, and with a
specified and controlled measurement system.
Notes:
• A requirement for calibration does not imply that the item
being calibrated can or should be adjusted.
• The calibration process may include, if necessary, calculation
of correction factors or adjustment of the instrument being
compared to reduce the magnitude of the inaccuracy.
• In some cases, minor repair such as replacement of batteries,
fuses, or lamps, or minor adjustment such as zero and span,
may be included as part of the calibration.
• Calibration does not include any maintenance or repair actions
except as just noted. See also: performance test, calibration
procedure Contrast with: calibration (2) and repair
Calibration – 2 A) Many manufacturers incorrectly use the term
calibration to name the process of alignment or adjustment of
an item that is either newly manufactured or is known to be out
of tolerance, or is otherwise in an indeterminate state. Many
calibration procedures in manufacturers’ manuals are actually
factory alignment procedures that only need to be performed if a
UUC is in an indeterminate state because it is being manufactured,
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appendix: calibration terminology a to z
1
is known to be out of tolerance, or after it is repaired. When used
this way, calibration means the same as alignment or adjustment,
which are repair activities and excluded from the metrological
definition of calibration.
(B) In many cases, IM&TE instruction manuals may use
calibration to describe tasks normally performed by the operator
of a measurement system. Examples include performing a selftest as part of normal operation or performing a self-calibration
(normalizing) a measurement system before use. When calibration
is used to refer to tasks like this, the intent is that they are part
of the normal work done by a trained user of the system. These
and similar tasks are excluded from the metrological definition of
calibration. Contrast with: calibration (1) See also: normalization,
self-calibration, standardization
Calibration activity or provider – A laboratory or facility – including
personnel – that perform calibrations in an established location or
at customer location(s). It may be external or internal, including
subsidiary operations of a larger entity. It may be called a calibration
laboratory, shop, or department; a metrology laboratory or
department; or an industry-specific name; or any combination or
variation of these.
Calibration certificate – (1) A calibration certificate is generally a
document that states that a specific item was calibrated by an
organization. The certificate identifies the item calibrated, the
organization presenting the certificate, and the effective date. A
calibration certificate should provide other information to allow
the user to judge the adequacy and quality of the calibration. (2)
In a laboratory database program, a certificate often refers to the
permanent record of the final result of a calibration. A laboratory
database certificate is a record that cannot be changed; if it is
amended later a new certificate is created. See also: calibration
report
Calibration procedure – A calibration procedure is a controlled
document that provides a validated method for evaluating and
verifying the essential performance characteristics, specifications,
or tolerances for a model of measuring or testing equipment.
A calibration procedure documents one method of verifying
the actual performance of the item being calibrated against its
performance specifications. It provides a list of recommended
calibration standards to use for the calibration; a means to record
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1
quantitative performance data both before and after adjustments;
and information sufficient to determine if the unit being calibrated
is operating within the necessary performance specifications. A
calibration procedure always starts with the assumption that the
unit under test is in good working order and only needs to have
its performance verified. Note: A calibration procedure does not
include any maintenance or repair actions.
Calibration program – A calibration program is a process of the
quality management system that includes management of the
use and control of calibrated inspection, and test and measuring
equipment (IM&TE), and the process of calibrating IM&TE used
to determine conformance to requirements or used in supporting
activities. A calibration program may also be called a measurement
management system (ISO 10012:2003).
Calibration report – A calibration report is a document that provides
details of the calibration of an item. In addition to the basic items
of a calibration certificate, a calibration report includes details of
the methods and standards used, the parameters checked, and the
actual measurement results and uncertainty. See also: calibration
certificate
Calibration seal – A calibration seal is a device, placard, or label that,
when removed or tampered with, and by virtue of its design and
material, clearly indicates tampering. The purpose of a calibration
seal is to ensure the integrity of the calibration. A calibration seal
is usually imprinted with a legend similar to “Calibration Void
if Broken or Removed” or “Calibration Seal – Do Not Break or
Remove.” A calibration seal provides a means of deterring the user
from tampering with any adjustment point that can affect the
calibration of an instrument and detecting an attempt to access
controls that can affect the calibration of an instrument. Note: A
calibration seal may also be referred to as a tamper seal.
Calibration standard – (See VIM, 6.1 through 6.9, and 6.13, 6.14;
and NCSL pages 36–38.) A calibration standard is an IM&TE
item, artifact, standard reference material, or measurement
transfer standard that is designated as being used only to perform
calibrations of other IM&TE items. As calibration standards
are used to calibrate other IM&TE items, they are more closely
controlled and characterized than the workload items they are
used for. Calibration standards generally have lower uncertainty
and better resolution than general-purpose items. Designation as a
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calibration standard is based on the use of the specific instrument,
however, not on any other consideration. For example, in a group
of identical instruments, one might be designated as a calibration
standard while the others are all general purpose IM&TE items.
Calibration standards are often called measurement standards. See
also: standard (measurement)
Combined standard uncertainty – The standard uncertainty of the
result of a measurement, when that result is obtained from the
values of a number of other quantities. It is equal to the positive
square root of a sum of terms. The terms are the variances or
covariances of these other quantities, weighted according to how
the measurement result varies with changes in those quantities.
(GUM, 2.3.4) See also: expanded uncertainty
Commercial of the shelf software – Software commercially available,
whose fitness for use is demonstrated by a broad spectrum of users.
Competence – For a laboratory, the demonstrated ability to perform
the tests or calibrations within the accreditation scope and to meet
other criteria established by the accreditation body. For a person,
the demonstrated ability to apply knowledge and skills. Note: The
word qualification is sometimes used in the personal sense, since
it is a synonym and has more accepted usage in the United States.
Confidence interval – A range of values that is expected to contain the
true value of the parameter being evaluated with a specified level
of confidence. The confidence interval is calculated from sample
statistics. Confidence intervals can be calculated for points, lines,
slopes, standard deviations, and so on. For an infinite (or very large
compared to the sample) population, the confidence interval is:
p (1 – p)
s
CI = x̄ ± t = ––– or CI = p ± –––––––––
n n
where
CI is the confidence interval,
n is the number of items in the sample,
p is the proportion of items of a given type in the population,
s is the sample standard deviation,
x is the sample mean, and
tis the Student’s T value for α ⁄2 and (n – 1) (α is the level of
significance).
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Correction (of error) – A correction is the value that is added to the
raw result of a measurement to compensate for known or estimated
systematic error or bias. (VIM, 3.15) Any residual amount is treated
as random error. The correction value is equal to the negative of
the bias. An example is the value calculated to compensate for
the calibration difference of a reference thermometer or for the
calibrated offset voltage of a thermocouple reference junction. See
also: bias, error, random error, systematic error
Corrective action – Corrective action is something done to correct a
nonconformance when it arises, including actions taken to prevent
reoccurrence of the nonconformance. Compare with: preventive
action
Coverage factor – A numerical factor used as a multiplier of the
combined standard uncertainty in order to obtain an expanded
uncertainty. (GUM, 2.3.6) The coverage factor is identified by
the symbol k. It is usually given the value 2, which approximately
corresponds to a probability of 95 percent for degrees of freedom
> 10’.
Deficiency – Nonfulfillment of conditions and/or criteria for
accreditation, sometimes referred to as a nonconformance.
Departure value – A term used by a few calibration laboratories to refer
to bias, error or systematic error. The exact meaning can usually be
determined from examination of the calibration certificate.
Equivalence – (A) Acceptance of the competence of other national
metrology institutes (NMI), accreditation bodies, and/or accredited
organizations in other countries as being essentially equal to the
NMI, accreditation body, and/or accredited organizations within
the host country.
(B) A formal, documented determination that a specific instrument
or type of instrument is suitable for use in place of the one originally
listed, for a particular application.
Error (of measurement) – (See VIM, 3.10, 3.12–3.14; and NCSL pages
11–13.) In metrology, error (or measurement error) is an estimate
of the difference between the measured value and the probable
true value of the object of the measurement. The error can
never be known exactly; it is always an estimate. Error may be
systematic and/or random. Systematic error (also known as bias)
may be corrected. See also: bias, correction (of error), random error,
systematic error
Gage R&R – Gage repeatability and reproducibility study, which
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(typically) employs numerous instruments, personnel, and
measurements over a period of time to capture quantitative
observations. The data captured are analyzed statistically to obtain
best measurement capability, which is expressed as an uncertainty
with a coverage factor of k = 2 to approximate 95 percent. The
number of instruments, personnel, measurements, and length of
time are established to be statistically valid consistent with the size
and level of activity of the organization.
GUM – An acronym commonly used to identify the ISO Guide to the
Expression of Uncertainty in Measurement. In the United States, the
equivalent document is ANSI/NCSL Z540-2-1997, U. S. Guide to
the Expression of Uncertainty in Measurement.
IM&TE – The acronym IM&TE refers to inspection, measuring,
and test equipment. This term includes all items that fall under
a calibration or measurement management program. IM&TE
items are typically used in applications where the measurement
results are used to determine conformance to technical or quality
requirements before, during, or after a process. Some organizations
do not include instruments used solely to check for the presence
or absence of a condition (such as voltage, pressure, and so on)
where a tolerance is not specified and the indication is not critical
to safety. Note: Organizations may refer to IM&TE items as MTE
(measuring and testing equipment), TMDE (test, measuring,
and diagnostic equipment), GPETE (general purpose electronic
test equipment), PME (precision measuring equipment), PMET
(precision measuring equipment and tooling), or SPETE (special
purpose electronic test equipment).
Interlaboratory comparison – Organization, performance, and
evaluation of tests or calibrations on the same or similar items
or materials by two or more laboratories in accordance with
predetermined conditions.
Internal audit – A systematic and documented process for obtaining
audit evidence and evaluating it objectively to verify that a
laboratory’s operations comply with the requirements of its quality
system. An internal audit is done by or on behalf of the laboratory
itself, so it is a first-party audit.
International Organization for Standardization (ISO) – An international
nongovernmental organization chartered by the United Nations
in 1947, with headquarters in Geneva, Switzerland. The mission
of ISO is “to promote the development of standardization and
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related activities in the world with a view to facilitating the
international exchange of goods and services, and to developing
cooperation in the spheres of intellectual, scientific, technological
and economic activity.” The scope of ISO’s work covers all fields of
business, industry and commerce except electrical and electronic
engineering. The members of ISO are the designated national
standards bodies of each country. (The United States is represented
by ANSI.) See also: ISO
International System of Units (SI) – A defined and coherent system of
units adopted and used by international treaties. (The acronym SI
is from the French Systéme International.) SI is international system
of measurement for all physical quantities. (Mass, length, amount
of substance, time, electric current, thermodynamic temperature,
and luminous intensity.) SI units are defined and maintained by
the International Bureau of Weights and Measures (BIPM) in Paris,
France. The SI system is popularly known as the metric system.
ISO – Iso is a Greek word root meaning equal. The International
Organization for Standardization chose the word as the short
form of the name, so it will be a constant in all languages. In this
context, ISO is not an acronym. (If the acronym was based on the
full name were used, it would be different in each language.) The
name also symbolizes the mission of the organization – to equalize
standards worldwide.
IT Infrastructure – The hardware and software such as networking
software and operation systems, which makes it possible for the
application to function.
Level of confidence – Defines an interval about the measurement result
that encompasses a large fraction p of the probability distribution
characterized by that result and its combined standard uncertainty,
and p is the coverage probability or level of confidence of the
interval. Effectively, the coverage level expressed as a percent.
Life cycle – All phases in the life of the system from initial requirements
until retirement including design, specification, programming,
testing, installation, operation, and maintenance.
Management review – The planned, formal, periodic, and scheduled
examination of the status and adequacy of the quality management
system in relation to its quality policy and objectives by the
organization’s top management.
Measurement – A set of operations performed for the purpose of
determining the value of a quantity. (VIM, 2.1)
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Measurement system – A measurement system is the set of equipment,
conditions, people, methods, and other quantifiable factors that
combine to determine the success of a measurement process.
The measurement system includes at least the test and measuring
instruments and devices, associated materials and accessories, the
personnel, the procedures used, and the physical environment.
Metrolog y – Metrology is the science and practice of measurement
(VIM, 2.2).
Mobile operations – Operations that are independent of an established
calibration laboratory facility. Mobile operations may include work
from an office space, home, vehicle, or the use of a virtual office.
Natural (physical) constant – A natural constant is a fundamental
value that is accepted by the scientific community as valid. Natural
constants are used in the basic theoretical descriptions of the
universe. Examples of natural physical constants important in
metrology are the speed of light in a vacuum (c), the triple point of
water (273.16 K), the quantum charge ratio (h/e), the gravitational
constant (G), the ratio of a circle’s circumference to its diameter
(p), and the base of natural logarithms (e).
NCSL international – Formerly known as the National Conference
of Standards Laboratories (NCSL). NCSL was formed in
1961 to “promote cooperative efforts for solving the common
problems faced by measurement laboratories. NCSL has member
organizations from academic, scientific, industrial, commercial
and government facilities around the world. NCSL is a nonprofit
organization, whose membership is open to any organization with
an interest in the science of measurement and its application in
research, development, education, or commerce. NCSL promotes
technical and managerial excellence in the field of metrology,
measurement standards, instrument calibration, and test and
measurement.”
Normalization, Normalize – See: self-calibration
Offset – Offset is the difference between a nominal value (for an
artifact) or a target value (for a process) and the actual measured
value. For example, if the thermocouple alloy leads of a reference
junction probe are formed into a measurement junction and placed
in an ice point cell, and the reference junction itself is also in the
ice point, then the theoretical thermoelectric emf measured at the
copper wires should be zero. Any value other than zero is an offset
created by inhomogeneity of the thermocouple wires combined
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with other uncertainties. Compare with: bias, error
On-site operations – Operations that are based in or directly supported
by an established calibration laboratory facility, but actually
perform the calibration actions at customer locations. This includes
climate-controlled mobile laboratories.
Performance Test – A performance test (or performance verification) is
the activity of verifying the performance of an item of measuring
and test equipment to provide assurance that the instrument is
capable of making correct measurements when it is properly used.
A performance test is done with the item in its normal operating
configuration. A performance test is the same as a calibration (1).
See also: calibration (1)
Policy – A policy defines and sets out the basic objectives, goals,
vision, or general management position on a specific topic. A
policy describes what management intends to have done regarding
a given portion of business activity. Policy statements relevant to
the quality management system are generally stated in the quality
manual. Policies can also be in the organization’s policy/procedure
manual. See also: procedure
Precision – Precision is a property of a measuring system or instrument.
Precision is a measure of the repeatability of a measuring system – how
much agreement there is within a group of repeated measurements
of the same quantity under the same conditions. (NCSL, page 26)
Precision is not the same as accuracy. (VIM, 3.5)
Preventive action – Preventive action is something done to prevent the
possible future occurrence of a nonconformance, even though such
an event has not yet happened. Preventive action helps improve the
system. Contrast with: corrective action
Procedure – A procedure describes a specific process for implementing
all or a portion of a policy. There may be more than one procedure
for a given policy. A procedure has more detail than a policy but
less detail than a work instruction. The level of detail needed
should correlate with the level of education and training of the
people with the usual qualifications to do the work and the amount
of judgment normally allowed to them by management. Some
policies may be implemented by fairly detailed procedures, while
others may only have a few general guidelines. Calibration: see
calibration procedure. See also: policy
Process owner – The person responsible for the business process.
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Proficiency testing – Determination of laboratory testing performance
by means of interlaboratory comparisons.
Quality manual – The quality manual is the document that describes
the quality management policy of an organization with respect to a
specified conformance standard. The quality manual briefly defines
the general policies as they apply to the specified conformance
standard and affirms the commitment of the organization’s top
management to the policy. In addition to its regular use by the
organization, auditors use the quality manual when they audit
the quality management system. The quality manual is generally
provided to customers on request. Therefore, it does not usually
contain any detailed policies and never contains any procedures,
work instructions, or proprietary information.
Random error – Random error is the result of a single measurement of
a value, minus the mean of a large number of measurements of the
same value. (VIM, 3.13) Random error causes scatter in the results
of a sequence of readings and, therefore, is a measure of dispersion.
Random error is usually evaluated by Type A methods, but Type
B methods are also used in some situations. Note: Contrary to
popular belief, the GUM specifically does not replace random
error with either Type A or Type B methods of evaluation. See also:
error Compare with: systematic error
Repair – Repair is the process of returning an unserviceable or
nonconforming item to serviceable condition. The instrument is
opened, or has covers removed, or is removed from its case and
may be disassembled to some degree. Repair includes adjustment
or alignment of the item as well as component-level repair. (Some
minor adjustment such as zero and span may be included as part of
the calibration.) The need for repair may be indicated by the results
of a calibration. For calibratable items, repair is always followed by
calibration of the item. Passing the calibration test indicates success
of the repair. Contrast with: calibration (1), repair (minor)
Repair (minor) – Minor repair is the process of quickly and economically
returning an unserviceable item to serviceable condition by doing
simple work using parts that are in stock in the calibration lab.
Examples include replacement of batteries, fuses, or lamps; or
minor cleaning of switch contacts; or repairing a broken wire; or
replacing one or two in-stock components. The need for repair may
be indicated by the results of a calibration. For calibratable items,
minor repair is always followed by calibration of the item. Passing
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the calibration test indicates success of the repair. Minor repairs are
defined as repairs that take no longer than a short time as defined
by laboratory management, and where no parts have to be ordered
from external suppliers, and where substantial disassembly of the
instrument is not required. Contrast with: calibration (1), repair
Reported value – One or more numerical results of a calibration
process, with the associated measurement uncertainty, as recorded
on a calibration report or certificate. The specific type and format
vary according to the type of measurement being made. In general,
most reported values will be in one of these formats:
• Measurement result and uncertainty. The reported value is
usually the mean of a number of repeat measurements. The
uncertainty is usually expanded uncertainty as defined in the
GUM.
• Deviation from the nominal (or reference) value and
uncertainty. The reported value is the difference between
the nominal value and the mean of a number of repeat
measurements. The uncertainty of the deviation is usually
expanded uncertainty as defined in the GUM.
• Estimated systematic error and uncertainty. The value may be
reported this way when it is known that the instrument is part
of a measuring system and the systematic error will be used
to calculate a correction that will apply to the measurement
system results.
Round robin – See: Interlaboratory Comparison
Scope of accreditation – For an accredited calibration or testing
laboratory, the scope is a documented list of calibration or testing
fields, parameters, specific measurements, or calibrations and
their best measurement, uncertainty. The scope document is an
attachment to the certificate of accreditation and the certificate is
incomplete without it. Only the calibration or testing areas that
the laboratory is accredited for are listed in the scope document,
and only the listed areas may be offered as accredited calibrations
or tests. The accreditation body usually defines the format and
other details.
Self-calibration – Self-calibration is a process performed by a user for
the purpose of making an IM&TE instrument or system ready
for use. The process may be required at intervals such as every
power-on sequence; or once per shift, day, or week of continuous
operation; or if the ambient temperature changes by a specified
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amount. Once initiated, the process may be performed totally by the
instrument or may require user intervention and/or use of external
calibrated artifacts. The usual purpose is accuracy enhancement
by characterization of errors inherent in the measurement system
before the item to be measured is connected. Self-calibration is
not equivalent to periodic calibration (performance verification)
because it is not performed using a calibration procedure and does
not meet the metrological requirements for calibration. Also, if
an instrument requires self-calibration before use, then that will
also be accomplished at the start of a calibration procedure. Selfcalibration may also be called normalization or standardization.
Compare with: calibration (2.B) Contrast with: calibration (1)
Specification – In metrology, a specification is a documented statement
of the expected performance capabilities of a large group of
substantially identical measuring instruments, given in terms of
the relevant parameters and including the accuracy or uncertainty.
Customers use specifications to determine the suitability of a
product for their own applications. A product that performs
outside the specification limits when tested (calibrated) is rejected
for later adjustment, repair, or scrapping.
Standard (document) – A standard (industry, national, government, or
international standard; a norme) is a document that describes the
processes and methods that must be performed in order to achieve
a specific technical or management objective, or the methods for
evaluation of any of these. An example is ANSI/NCSL Z540-11994, a national standard that describes the requirements for the
quality management system of a calibration organization and the
requirements for calibration and management of the measurement
standards used by the organization.
Standard (measurement) – A standard (measurement standard,
laboratory standard, calibration standard, reference standard; an
étalon) is a system, instrument, artifact, device, or material that
is used as a defined basis for making quantitative measurements.
The value and uncertainty of the standard define a limit to the
measurements that can be made: a laboratory can never have better
precision or accuracy than its standards. Measurement standards
are generally used in calibration laboratories. Items with similar
uses in a production shop are generally regarded as working-level
instruments by the calibration program.
Primary standard. Accepted as having the highest metrological
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qualities and whose value is accepted without reference to other
standards of the same quantity. Examples: triple point of water cell
and caesium beam frequency standard.
Transfer standard. A device used to transfer the value of a
measurement quantity (including the associated uncertainty) from
a higher level to a lower level standard.
Secondary standard. The highest accuracy level standards in a
particular laboratory generally used only to calibrate working
standards. Also called a reference standard.
Working standard. A standard that is used for routine calibration
of IM&TE. The highest level standards, found in national and
international metrology laboratories, are the realizations or
representations of SI units. See also: calibration standard
Standard operating procedure (SOP) – A term used by some organizations
to identify policies, procedures, or work instructions.
Standard reference material – A standard reference material (SRM) as
defined by NIST “is a material or artifact that has had one or more
of its property values certified by a technically valid procedure,
and is accompanied by, or traceable to, a certificate or other
documentation which is issued by NIST… Standard reference
materials are…manufactured according to strict specifications
and certified by NIST for one or more quantities of interest.
SRMs represent one of the primary vehicles for disseminating
measurement technology to industry.”
Standard uncertainty – The uncertainty of the result of a measurement,
expressed as a standard deviation. (GUM, 2.3.1)
Standardization – See: self-calibration.
Systematic error – A systematic error is the mean of a large number of
measurements of the same value minus the (probable) true value
of the measured parameter. (VIM, 3.14) Systematic error causes the
average of the readings to be offset from the true value. Systematic
error is a measure of magnitude and may be corrected. Systematic
error is also called bias when it applies to a measuring instrument.
Systematic error may be evaluated by Type A or Type B methods,
according to the type of data available. Note: Contrary to popular
belief, the GUM specifically does not replace systematic error with
either Type A or Type B methods of evaluation. (3.2.3, note) See
also: bias, error, correction (of error) Compare with: random error
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System owner – The person responsible for the availability, and
maintenance of a computerised system and for the security of the
data residing on that system.
Test accuracy ratio – (1) In a calibration procedure, the test accuracy
ratio (TAR) is the ratio of the accuracy tolerance of the unit under
calibration to the accuracy tolerance of the calibration standard
used. (NCSL, page 2)
TAR = UUT_tolerance
STD_tolerance
The TAR must be calculated using identical parameters and units
for the UUC and the calibration standard. If the accuracy tolerances
are expressed as decibels, percentage, or another ratio, they must
be converted to absolute values of the basic measurement units.
(2) In the normal use of IM&TE items, the TAR is the ratio of
the tolerance of the parameter being measured to the accuracy
tolerance of the IM&TE. Note: TAR may also be referred to as the
accuracy ratio or (incorrectly) the uncertainty ratio.
Test uncertainty ratio – In a calibration procedure, the test uncertainty
ratio (TUR) is the ratio of the accuracy tolerance of the unit under
calibration to the uncertainty of the calibration standard used.
(NCSL, page 2)
TUR = UUT_tolerance
STD_uncert
The TUR must be calculated using identical parameters and units
for the UUC and the calibration standard. If the accuracy tolerances
are expressed as decibels, percentage, or another ratio, they must be
converted to absolute values of the basic measurement units. Note:
The uncertainty of a measurement standard is not necessarily the
same as its accuracy specification.
Third Party – Parties
Tolerance – A tolerance is a design feature that defines limits within
which a quality characteristic is supposed to be on individual parts;
it represents the maximum allowable deviation from a specified
value. Tolerances are applied during design and manufacturing. A
tolerance is a property of the item being measured. Compare with:
specification, uncertainty
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Traceable, traceability – Traceability is a property of the result of a
measurement, providing the ability to relate the measurement result
to stated references, through an unbroken chain of comparisons
each having stated uncertainties. (VIM, 6.10) Traceability is a
demonstrated or implied property of the result of a measurement
to be consistent with an accepted standard within specified limits
of uncertainty. (NCSL, pages 42–43) The stated references are
normally the base or supplemental SI units as maintained by a
national metrology institute; fundamental or physical natural
constants that are reproducible and have defined values; ratio type
comparisons; certified standard reference materials; or industry
or other accepted consensus reference standards. Traceability
provides the ability to demonstrate the accuracy of a measurement
result in terms of the stated reference. Measurement assurance
methods applied to a calibration system include demonstration
of traceability. A calibration system operating under a program
controls system only implies traceability. Evidence of traceability
includes the calibration report (with values and uncertainty)
of calibration standards, but the report alone is not sufficient.
The laboratory must also apply and use the data. A calibration
laboratory, a measurement system, a calibrated IM&TE, a
calibration report, or any other thing is not and be traceable to a
national standard. Only the result of a specific measurement can
be said to be traceable, provided all of the conditions just listed are
met. Reference to a NIST test number is specifically not evidence of
traceability. That number is merely a catalog number of the specific
service provided by NIST to a customer so it can be identified on
a purchase order.
Transfer measurement – A transfer measurement is a type of method that
enables making a measurement to a higher level of resolution than
normally possible with the available equipment. Common transfer
methods are differential measurements and ratio measurements.
Transfer standard – A transfer standard is a measurement standard used
as an intermediate device when comparing two other standards.
(VIM, 6.8) Typical applications of transfer standards are to transfer
a measurement parameter from one organization to another, from
a primary standard to a secondary standard, or from a secondary
standard to a working standard in order to create or maintain
measurement traceability. Examples of typical transfer standards
are DC volt sources (standard cells or zener sources), and singlevalue standard resistors, capacitors, or inductors.
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Type A evaluation (of uncertainty) – Type A evaluation of measurement
uncertainty is the statistical analysis of actual measurement results
to produce uncertainty values. Both random and systematic error
may be evaluated by Type A methods. (GUM, 3.3.3 through
3.3.5) Uncertainty can only be evaluated by Type A methods if
the laboratory actually collects the data.
Type B evaluation (of uncertainty) – Type B evaluation of measurement
uncertainty includes any method except statistical analysis of
actual measurement results. Both random and systematic error
may be evaluated by Type B methods. (GUM, 3.3.3 through 3.3.5)
Data for evaluation by Type B methods may come from any source
believed to be valid.
Uncertainty – Uncertainty is a property of a measurement result
that defines the range of probable values of the measurand.
Total uncertainty may consist of components that are evaluated
by the statistical probability distribution of experimental data
or from assumed probability distributions based on other data.
Uncertainty is an estimate of dispersion; effects that contribute
to the dispersion may be random or systematic. (GUM, 2.2.3)
Uncertainty is an estimate of the range of values that the true value
of the measurement is within, with a specified level of confidence.
After an item that has a specified tolerance has been calibrated
using an instrument with a known accuracy, the result is a value
with a calculated uncertainty. See also: Type A evaluation, Type B
evaluation
Uncertainty budget – The systematic description of known uncertainties
relevant to specific measurements or types of measurements,
categorized by type of measurement, range of measurement, and/
or other applicable measurement criteria.
UUC, UUT – The unit under calibration or the unit under test – the
instrument being calibrated. These are standard generic labels for
the IM&TE item that is being calibrated, which are used in the text
of the calibration procedure for convenience. Also may be called
device under test (DUT) or equipment under test (EUT).
Validation – Substantiation by examination and provision of objective
evidence that verified processes, methods, and/or procedures are
fit for their intended use.
Verification – Confirmation by examination and provision of objective
evidence that specified requirements have been fulfilled.
VIM – An acronym commonly used to identify the ISO International
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Vocabulary of Basic and General Terms in Metrology. (The acronym
comes from the French title.)
Work Instruction – In a quality management system, a work instruction
defines the detailed steps necessary to carry out a procedure.
Work instructions are used only where they are needed to ensure
the quality of the product or service. The level of education and
training of the people with the usual qualifications to do the
work must be considered when writing a work instruction. In a
metrology laboratory, a calibration procedure is a type of work
instruction.
1. Bucher, Jay L. 2004. The Metrology Handbook. Milwaukee: ASQ
Quality Press.
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as automotive, aviation, contractor engineering,
education, food and beverage, manufacturing,
marine, metal and mining, nuclear, oil and gas,
petrochemical and chemical, pharmaceutical,
power and energy, and pulp and paper.
• For customers with requirements for accuracy,
versatility, efficiency, ease-of-use and reliability.
• Beamex’s Accredited Calibration Laboratory
is accredited and approved by FINAS (Finnish
Accreditation Service). FINAS is a member of all
Multilateral Recognition Agreements / Mutual
Recognition Arrangements (MLA/MRA) signed by
European and other international organizations,
i.e. European co-operation for Accreditation
(EA), International Laboratory Accreditation
Cooperation (ILAC) and International
Accreditation Forum Inc. (IAF).
Why is Beamex better
Accuracy assured
Accuracy is assured when you
decide to purchase a Beamex®
calibrator. They are all delivered with
a traceable, accredited calibration
certificate.
Integrated calibration solutions
Beamex calibrators, workstations,
calibration software and professional
services form an integrated,
automated system.
Industry pioneer
with global presence
A forerunner in developing
high-quality calibration equipment
and software, with global customer
base and partner network.
High customer satisfaction
Constantly improving understanding
of customer needs and developing
solutions to meet them.
Support
Installation, training, validation,
system integration, database
conversion, Help Desk and
re-calibration services available.
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