NMI P 100
Guide to Carrying out a 6B/0 Analysis
First edition — March 1998
Second edition — June 2003 (renamed NSC P 100)
Second edition, first revision — July 2004 (renamed NMI P 100)
Bradfield Road, Lindfield, NSW 2070
PO Box 264, Lindfield, NSW 2070
Telephone: (61 2) 8467 3600
Facsimile: (61 2) 8467 3610
Web page: http://www.measurement.gov.au
© Commonwealth of Australia 1998
CONTENTS
Preface....................................................................................................................................... iv
1.
Introduction ...................................................................................................................... 1
2.
Terminology ..................................................................................................................... 1
3.
Scope ................................................................................................................................ 1
3.1 Converters May ....................................................................................................... 1
3.2 Converters May Not ................................................................................................ 1
3.3 Manufactures May .................................................................................................. 1
3.4 Manufacturers May Not: ......................................................................................... 2
4.
Responsibilities ................................................................................................................ 2
5.
6B/0 Analysis ................................................................................................................... 2
6.
Markings ........................................................................................................................... 6
7.
6B/0 Analysis Report........................................................................................................ 6
Appendix 1. Sample Calculations .............................................................................................. 7
Appendix 2. Sample 6B/0 Analysis Reports .............................................................................. 9
iii
PREFACE
General Certificate 6B/0. Weighing Instruments for Static Loads Not Less than 100 kg gives
manufacturers and converters the flexibility to use a range of approved load cells and
indicators in the manufacture and conversion of non-automatic weighing instruments which
have a maximum capacity greater than 100 kg and which are used for trade purposes, without
having to obtain specific approval for each basework/indicator/load cell combination.
General Certificate 6B/0 also limits this flexibility, to ensure that instruments and the modules
of which they are comprised comply with their approved parameters.
NMI P 100. Guide to Carrying out a 6B/0 Analysis has been developed to enable
manufacturers and converters to carry out an assessment to determine whether a particular
instrument complies with the requirements of General Certificate 6B/0. Contact NMI if
compliance is still not clear after an analysis has been made.
In this second edition the text has been updated and it has been renamed as NMI P 100.
Notes
You must have a 6B/0 certificate to either manufacture or convert a weighing instrument.
If you are a licensed certifier you have to ensure that the analysis report is available when the
instrument is certified.
Trade measurement authorities can supervise the validity of the 6B/0 analysis report in the
same way as they supervise other responsibilities of a licensed certifier.
Useful Resource
A list of NMI-approved patterns of measuring instruments.
General Certificate 6B/0. Weighing Instruments for Static Loads Not Less than 100 kg.
General Supplementary Certificate of Approval S1/0/A. Electronic Indicating and Printing
Devices.
iv
1.
INTRODUCTION
3.2 Converters May Not


NMI P 100 is set out in steps which provide a
logical progression through a 6B/0 analysis.
It also includes additional information
decided upon by NMI, but not explicitly
included in General Certificate 6B/0. Any
unusual 6B/0 analyses which are not
specifically covered by NMI P 100 should be
referred to NMI.
2.


TERMINOLOGY
Converter
The organisation listed as the applicant in a
conversion certificate of approval, for
example 6B/999.
3.3 Manufactures May
Manufacturer
The organisation listed as the applicant in a
certificate of approval for the pattern of an
instrument, for example 6/9C/999.
3.

Perform the same tasks as converters
(see above).

Install a different type of load cell from
that specified in the certificate of
approval (overhead track-type
instruments excluded). This load cell(s)
must be mounted as described in the
supplementary certificate of approval
for the component.

Manufacture instruments over a range
of maximum capacities. The maximum
capacity of the instrument must fall
within one of the ranges given in
Table 1 and must be in the same range
as the maximum capacity listed in the
certificate of approval for the
instrument. For example, an instrument
marked NMI 6/10B/*** for which the
approval specifies a maximum capacity
of 60 000 kg may be constructed with a
maximum capacity of between
15 000 kg and 149 000 kg.
SCOPE
General Certificate 6B/0 applies to the
conversion and manufacture of instruments.
Before beginning the analysis ensure that
the operation complies with the scope
(clause 2) of General Certificate 6B/0. Pay
particular attention to the paragraph
beginning ‘This approval permits …’.
In addition the following apply:
3.1 Converters May





Replace an indicator on any existing
instrument with the same or different
suitable indicator.
Replace the load cell on a lever/load
cell instrument with the same or
different suitable load cell.
Replace load cells on a full load cell
instrument with the same type of load
cell.
Change the scale interval on an
instrument, including making the
instrument multi-interval or multiple
range.
Convert a mechanical lever instrument
to a lever/load cell instrument.
7/04
Manufacture new instruments.
Increase the maximum capacity of an
instrument.
Replace load cells on a full load cell
instrument with a different type of load
cell, for example replace a
compression-type load cell with a
single point beam-type load cell.
Change the principle of operation of an
instrument, for example convert a
lever/load cell instrument to a full load
cell instrument.
Table 1. Maximum capacity ranges of
instruments
From 100 kg up to 1 499 kg
From 1 500 kg up to 14 999 kg
From 15 000 kg up to 149 999 kg
150 000 kg and above
1
NMI P 100

(b) work carried out is of a satisfactory
standard and complies with the relevant
safety and engineering codes and
standards; and
Manufacture instruments with
platform-type load receptors with up to
the maximum number of load cells as
specified in the certificate of approval
provided there are always at least four
load cells and the number of cells are
in multiples of two.
(c) they understand the conditions of
approval on page 2 of General
Certificate 6B/0.
Written approval may be given to another
organisation to manufacture an instrument on
behalf of the manufacturer or to convert an
instrument on behalf of the converter. In either
case, the manufacturer or converter (whichever
is applicable) is responsible for ensuring that
such instruments purporting to comply with a
certificate of approval are constructed in
accordance with that certificate.
3.4 Manufacturers May Not:

Change the type or model of load cell
used in an overhead track-type
instrument.

Use a multiple-cell arrangement for the
load at a single point unless this
arrangement is approved by NMI.

Manufacture platform-type instruments
which have more than two load cells in
the width direction of the platform unless
the certificate of approval specifically
allows for this construction.

Referring to the National Measurement Act
1960, section 19B, about offences:
A person shall not falsely represent:
(a) that a pattern of a measuring
instrument is in accordance with a
pattern approved under the regulations
as a pattern of a measuring instrument
suitable for use for trade; or
Manufacture a hopper-type instrument
if no such instrument is included in the
certificate of approval.
Notes:
4.
(1) Non-vertical cylindrical hoppertype load receptor instruments
must be manufactured using the
same number of load cells as
described in their certificate of
approval.
(b) that a measuring instrument is in
accordance with a pattern so approved.
(2) Vertical cylindrical hopper or tanktype load receptor instruments,
where the hopper is directly
supported by load cells, can be
manufactured with three to five
load cells.
If at any stage the requirements of any of
the following steps are not met, then the
analysis has failed.
Penalty: $ 6 000
5.
Steps marked ‘for manufacture only’ are
not applicable to conversion of instruments.
(1) Ensure that the instrument has a certificate
of approval. For the manufacture of an
instrument, the instrument shall be
designed in accordance with the relevant
current certificate of approval for the
instrument. For the conversion of an
existing instrument, the basework of the
instrument to be converted shall be
marked with an approval number, for
example 6/10B/***.
RESPONSIBILITIES
Both manufacturers and converters are
responsible for ensuring that:
(a) any operation carried out using 6B/0
complies with General Certificate
6B/0, with particular reference to the
scope and analysis;
7/04
6B/0 ANALYSIS
2
NMI P 100
(2) Determine the following specifications
for the proposed instrument:
 the maximum capacity;
 the value of the verification scale
interval (e);
 the number of verification scale
intervals;
 the number of load cells;
 if there are six or more load cells,
the H/J ratio;
 the dead load of the load receptor, or
the dead load force applied to the
load cell if a lever/load cell;
 if applicable, the length and width of
the platform; and
 if a multiple-range or multi-interval
instrument, the capacity values of
the ranges and the verification scale
interval (e1, e2 etc) for each range.
(6) Obtain the following load cell data
from its supplementary certificate or
our website:
 manufacturer, model and NMI
number;
 certificate current status;
 maximum capacity (kg);
 maximum number of verification
scale intervals;
 minimum value of verification scale
interval (kg);
 output rating, nominal (mV/V);
 input impedance, nominal ();
 supply voltage (V); and
 if linearisation is required, the least
number of linearisation points.
Note: If multiple-range or multiinterval, the minimum dead
load output return in
kilograms is required.
(3) For manufacture only. Carefully read
the certificate of approval for the
instrument. Ensure that the proposed
type of load receptor conforms to the
certificate. For example if the
instrument is only approved for a
platform-type receptor, then a hoppertype receptor cannot be made. Ensure
that the proposed load cell mounting
method is the same as in the certificate
of approval for the instrument or in the
supplementary certificate of approval
for the load cell.
(7) Obtain the following indicator data
from its supplementary certificate or
our website:
 manufacturer, model and NMI
number;
 certificate current status;
 maximum number of verification
scale intervals;
 minimum sensitivity (mV/scale
interval);
 excitation voltage (V);
 minimum load impedance ();
 maximum excitation current (mA);
and
 if the indicator has a linearisation
facility, the number of linearisation
points.
(4) For manufacture only. The maximum
capacity of the manufactured
instrument must fall within one of
ranges specified in Table 1 and must be
in the same range as the maximum
capacity listed in the certificate of
approval for the instrument.
(8) Check that the status of the certificates
of approval are correct for the type of
operation to be undertaken (see Table 2).
(5) For manufacture only. If the instrument
has a platform-type load receptor, it may
have less load cells than the number of
load cells in the instrument certificate of
approval, provided there are always at
least four load cells and the number of
cells is in multiples of two.
7/04
3
NMI P 100
Table 2. Currency status of certificates of approval
Operation
Manufacture of a new
instrument
Certificate of
approval for the
instrument
Supplementary
certificate of
approval for the
load cell
Supplementary
certificate of
approval for the
indicator
current
current
current
Conversion of an existing instrument
Change all load cell(s)
current or expired
current
current or expired
Change indicator
current or expired
current or expired
current
Change all load cell(s)
and indicator
current or expired
current
current
Notes:
 Current means that a certificate has not
reached its expiry date (or review date
if an expiry date is not stated), nor has
it been cancelled or withdrawn.
Expired means that a certificate has
either reached its expiry date or has
been cancelled. Certificates which have
been withdrawn are not valid for use
for trade under any circumstances.
 If a certificate has expired it may be
that either a notification of change
notice has been issued extending the
expiry date of the certificate or the
certificate may have been reviewed and
another one reissued. Check this by
contacting NMI.
 If a certificate has been reissued, check
the data on the new certificate as it may
have changed from that appearing in
the reviewed certificate.
 A load cell or indicator from an
existing approved instrument can be
used regardless of its currency status
providing it has a corresponding
supplementary certificate of approval.
 Policy on use of expired load cells used
for repair (see General Certificate
6B/0, Change No 2).
(9) From the load cell data, check to see if
the load cell requires linearisation and if
so the number of linearisation points
7/04
required. The indicator used must have
the facility for linearisation for at least
the number of points required otherwise
it cannot be used. For example:
 according to supplementary
certificate SXXX, model 111 load
cells ‘shall only be used with an
indicator incorporating at least
three-point linearisation’;
 the model 222 indicator can be used
with the above load cells as it
‘incorporates a linearisation facility
having ten intermediate points’
(refer SYYY); however
 the model 333 indicator cannot be
used with the above load cells as it
is ‘fitted with a programmable
single-point linearisation facility’
(refer SZZZ).
(10) Ensure the load receptor complies with
General Certificate 6B/0, clause 3.2.
(11) Carry out the necessary calculations as set
out in General Certificate 6B/0, clause 6.
Refer to Appendix 1 for sample
calculations. Instruments having different
configurations to the instrument in the
sample calculations may have different
calculations. Therefore, it is important to
carefully read the following steps.
4
NMI P 100
6.1 Dead Load
6.4 Minimum Value of Verification Scale
Interval for the Load Cell
This equation ensures that a nominal load is
applied to the load cells.
A load cell is approved for a minimum
force below which it is not accurate. This
equation determines if the load cell is being
used above the minimum value.
6.2 Loaded Capacity of the Load Cell(s)
This equation ensures the load cell(s) are
not overloaded. For six or more load cells
on a weighbridge the H/J ratio is used to
ensure that the spacing between the cells is
sufficient to prevent overloading of any of
the cells. The calculations are based on a
uniformly distributed load.
Note: For multi-interval or multiple-range
instruments the verification scale
interval for the instrument is the
value of the verification scale
interval for the first interval or first
range.
The calculations for a hopper apply only for
instruments with less than six cells.
6.5 Minimum Sensitivity of the Digital
Indicator
6.3 Number of Verification Scale Intervals
for the Instrument
This equation determines if the indicator is
being used to measure voltages above the
minimum value for which it is approved as
supplied by the load cell.
Load cells and indicators are designed to be
used for a maximum number of scale
intervals and this clause ensures the load
cell and indicator are approved for the
number of verification scale intervals
required. In addition apply the limits shown
in Table 3 (based on NMI R 76-1,
clause 3.2).
For multi-interval or multiple-range
instruments the approved minimum
sensitivity shall be less than:
excitation volts  load cell sensitivity  load ratio
number of verification scale intervals for the
instrument
For multi-interval instruments the
following equation must be satisfied:
DR  0.5e1 / R√N
where load ratio equals:
maximum capacity of the instrument
R  N  load cell capacity
For multiple-range instruments the
following equation must be satisfied:
DR  e1 /R√N
6.6 Load Cell Impedance
These equations determine if the indicator
has enough power to run the cell(s)
proposed.
where
DR is the minimum dead load output return
value for the load cell;
e1 is the verification scale interval for the
first range;
R is the lever ratio; and
N is the number of load cells.
Table 3. Verification scale intervals and number of verification scale intervals in
relation to the accuracy class of an instrument
Accuracy
class
3
4
Verification scale
interval (e)
5 g
5 g
Minimum number of
verification scale intervals
500
100
Maximum number of
verification scale intervals
10 000
1 000
Note: The accuracy class is determined by the accuracy class of the indicator and basework,
with the lower of the two being the accuracy class of the overall instrument.
7/04
5
NMI P 100
6.
MARKINGS
Ensure that the instrument is marked as
described in clause 5 of General Certificate
6B/0.
7.
6B/0 ANALYSIS REPORT
The results of the analysis are to be
presented in a 6B/0 analysis report and may
contain the same information and may
follow the same format as the sample report
in Appendix 2. The report should be filed
by the organisation carrying out the analysis
and be produced on demand by NMI or
trade measurement personnel.
Note: A 6B/0 analysis report can apply to
more than one instrument. Any
number of instruments of the same
specifications can be manufactured
using the one analysis report.
7/04
6
NMI P 100
APPENDIX 1. SAMPLE CALCULATIONS
The following calculations are for the manufacture of a multiple-interval platform-type
instrument using four load cells.
DATA
Instrument Data
Certificate of approval
Manufacturer and model
Certificate expiry date
Maximum capacity
Verification scale interval over first range (e1)
Verification scale interval over second range (e2 )
Number of e1
Number of e2
Number of load cells (N)
H/J ratio
Dead load
Length of platform
Width of platform
6/9C/999
ABC Company, model XYZ-1
_ _/_ _/_ _
11 500 kg
2 kg (from 0 to 2 500 kg)
5 kg (from 2 500 to 11 500 kg)
1 250
2 300
4
n/a
150 kg/m length of platform
1.8 m
1.5 m
Load Cell Data
Certificate of approval
Manufacturer and model
Certificate expiry date
Maximum capacity
Maximum number of verification scale intervals
Minimum value of verification scale interval
Minimum dead load output return value
Output rating
Input impedance
Supply voltage
S XXX
Company A, model 111
1/6/1999
3 000 kg
2 500
0.36 kg
0.216 kg
1.75 mV/V
390 
10–17 V
Indicator Data
Certificate of approval
Manufacturer and model
Certificate expiry date
Maximum number of verification scale intervals
Minimum sensitivity
Excitation voltage
Minimum load impedance
Maximum excitation current
7/04
7
S YYY
Company B, model 222
1/8/2000
5 000
0.7  10-3 mV/scale interval
10 V dc
75 
135 mA
NMI P 100
CALCULATIONS
The following calculations are carried out using the formulae in clause 6 of General
Certificate 6B/0.
6.1 Dead Load
1.8 m  150 kg/m / 4 > 0.01  3 000 kg
 67.5 kg > 30
true therefore acceptable
6.2 Loaded Capacity of the Load Cell(s)
3 000 kg > (11 500 kg + 1.8 m  150 kg/m) / 4
 3 000 kg > 2 942.5 kg
true therefore acceptable
6.3 Number of Verification Scale Intervals for the Instrument
Number of e1 and e2 < maximum number of verification scale
intervals for load cell
 1 250 and 2 300 < 2 500
true therefore acceptable
Number of e1 and e2 < maximum number of verification scale
intervals for indicator
 1 250 and 2 300 < 5 000
true therefore acceptable
Refer to Table 3 for class 3
Number of e1 and e2 > 500 and < 10 000
 1 250 and 2 300 > 500 and < 10 000
true therefore acceptable
For multi-interval 0.216 kg  0.5  2 kg / 1√4
 0.216 kg  0.5 kg
true therefore acceptable
6.4 Minimum Value of Verification Scale Interval for the Load Cell
0.36 kg < 2 kg / 1√4
 0.36 kg < 1 kg
true therefore acceptable
6.5 Minimum Sensitivity of the Digital Indicator
0.7  10-3 mv/scale interval < (10 V  1.75 mV/V  2 kg) /
(1  4  3 000 kg)
 0.7  10-3 mv/scale interval < 2.92  10-3 mv/scale interval
true therefore acceptable
6.6 Load Cell Impedance
390  > 10 V  4 / 0.135 A
 390  > 296 
7/04
true therefore acceptable
8
NMI P 100
APPENDIX 2. SAMPLE 6B/0 ANALYSIS REPORTS
Note: This report should be on company letterhead and signed in pen.
Organisation carrying out analyses
6B/0 conversion certificate number
Date
Report reference number
XYZ Weighing Company
6B/999
26 June 1996
Instrument Specifications
NMI number
Model type
Type of construction
Instrument maximum capacity
Value of the verification scale interval e1
Value of the verification scale interval e2
Platform length
Platform width
Dead load
Number of load cells
Lever ratio
H/J ratio
Load cell
Indicator
6/9C/999
ABC Company, model XYZ-1
Conversion of existing instrument.
11 500 kg
2 kg (from 0 to 2 500 kg)
5 kg (from 2 500 to 11 500 kg)
1.8 m
1.5 m
150 kg
4
n/a
n/a
Company A, model 111, NMI number S XXX
Company B, model 222, NMI number S YYY
Results of Calculations
Dead load
Loaded capacity of the load cell(s)
Number of verification scale intervals for the instrument
Minimum value of verification scale intervals for the load cell(s)
Minimum sensitivity of the indicator
Load cell impedance
Indicator output current
acceptable
acceptable
acceptable
acceptable
acceptable
acceptable
acceptable
Expiry Dates
Instrument
Load cell
Indicator
acceptable
acceptable
acceptable
sign here
John Smith
Engineer
XYZ Weighing Company
Date
7/04
9
NMI P 100