Practical Interpretation of Unbroken
Chain in Metrological Traceability
as to VIM 3
Authors: Yi-Ting Chen, Lung-Hen Chow,
Liang-Hsing Chen, and Gwo-Sheng Peng
Center for Measurement Standards (CMS)
Industrial Technology Research Institute (ITRI)
1
Outline
1.
2.
3.
4.
5.
6.
Introduction
Definition of “Metrological traceability” in VIM 3
Typical Metrological Traceability Diagram
Additional Mathematical Description
Case study - Gauge Block Measurement
Discussion and Conclusion
2
Introduction
3
Introduction
• Clear the addresses of VIM
– ISO/IEC Guide 99:2007, “International vocabulary of
metrology — Basic and general concepts and associated
terms” cancels and replaces the old VIM:1999 .
• The term “Traceability” is replaced by “Metrological
traceability”
– a new definition as property of a measurement result
which can be related to a reference
– an evidence of measurands tracing to the primary
standards which can realize the SI units
– a documented unbroken chain of calibrations
4
Introduction
• National Measurement Laboratory (NML, the NMI
in Taiwan) has operated its mission since 1987.
Effective knowledge transfer has become an
essential issue.
• In dealing with definition of “metrological
traceability” in VIM 3, additional mathematical
description is taken to enhance the practical
interpretation of the definition.
• Gauge block measurement is demonstrated for
such purpose at NML.
5
Definition of “Metrological
traceability” in VIM 3
6
Definition of metrological traceability in
VIM 3
Definition of this term in VIM 3 :
2.41 metrological traceability
Property of a measurement result whereby the result
can be related to a reference through a documented
unbroken chain of calibrations, each contributing to the
measurement uncertainty.
2007
7
Metrological traceability
Property of a measurement result whereby the result can be related to a
reference through a documented unbroken chain of calibrations, each
contributing to the measurement uncertainty.
Reference
Measurement
standard
Measurement
procedure
Measurement
unit
Calibration
document
Calibration
Measurand
document
Calibration
document
Measurement
Result
Measurement result
Measurement
uncertainty
&
Measured
quantity value
8
Six important elements in ILAC P-10
The International Laboratory Accreditation Cooperation
(ILAC) also proposed six important elements to confirm
the definition of “metrological traceability” :
1. an unbroken chain
2. uncertainty of measurement
3. documentation
4. competence
5. reference to SI units
6. calibration intervals
2.41 Metrological Traceability :
Property of a measurement result
whereby the result can be related to
a reference5 through a documented3
unbroken chain1 of calibrations6,
each contributing to the
measurement uncertainty2.
9
Typical metrological traceability
diagram
10
Typical metrological traceability diagram
• Hardness traceability chain
in Metrologia 47(2010) S59–S66
(Traceability in hardness measurements: from the definition to industry)
11
Typical approach of NML’s metrological
Traceability Diagram
• Measurement System Validation Procedure (MSVP).
•• The
in figures
cannot
fully cover the
Fortraceability
a specificillustration
measured
quantity
of calibration
at
aforementioned six important elements of metrological
NML, there will be two documents:
traceability.
– Instrument Calibration Technique (ICT)
– Measurement System Validation Procedure
(MSVP).
Gauge block comparator
measurement traceability diagram
Mass measurement system
traceability diagram
12
Additional Mathematical
Description
13
Additional Mathematical Description
• Combine “mathematical measurement equation”
with typical metrological traceability diagram to
reinforce the evidence of “unbroken chain of
calibrations”.
• In order to really focus on the property of
measurement result as metrological traceability
defined in VIM 3 ,
we shall emphasize the output
quantity in the measurement
model or equation.
14
Case study
- Gauge Block Measurement
15
Metrological traceability of gauge block measurement
SI unit
length (m)
MeP Fequency Stabilized laser,
fr , (Iodine stabilized He-Ne laser )
Frequency Stabilized
Lasers calibration
system
Fequency stabilized laser,
Frequency
f λ, wavelength：
deviation, △f (kHz)
632.990 904 4 nm
Gauge Block
Interferometer
calibration system
Standard gauge block, Lr
Deviation, d2 (mm)
0.5 mm to 100 mm
Gauge Block
Comparator
calibration system
Gauge block, LX
Measured
0.5 mm to 100 mm
difference, d1 (mm)
Gauge block
measurement
result
an unbroken
1.
chain
5. reference to SI units
SI unit : length (m)
c
  0 , f  fr  Δ f
(4)
nf
f：frequency value of calibrated laser
f r：frequency value of standard laser
f：frequency deviation of beat frequency measuremen t
n ： refractive index
c0：velocity of light in vacuum

(   )
(3)
2
d 2 : deviation from gauge block interferom eter
 : laser vacu um wavelengt h
 : interferen ce stripe number from measuremen t
 : interferen ce stripe number from calculatio n
Lr  LN  d 2
(2)
Lr：measuremen t result of standard gauge block
LN：nominal value of standard gauge block
d：
2 deviation from gauge block interferom eter
Lx  Lr  d1
(1)
L x：measuremen t result of calibrated gauge block
L r：measuremen t result of standard gauge block
d1 ：measuremen t difference from gauge block comparator
 LN  d1 parameter
d2
 TheLxleft-hand
of the equation is
L x：measuremen
t result of calibrated
gauge are
block
unknown
and the right-hand
parameters
known.
LN： nominal v alue
of standard
block chain is
 In mathematical
approach,
angauge
unbroken
d1： mesurement
f erencef romgauge
block
demonstrated
anddifmeasurement
result
ofcomparator
each step
16
d
：
dev
iation
f
rom
gauge
block
interf
erom
eter
2
traced
to the measurand of the previous step.
d2 
Metrological traceability of auxiliary parameters
SI unit
length (m)
K
K
Temperature
standard
Temperature
standard

SI unitsK Pa
Pa
MeP Stabilized laser
Frequency Stabilized
Lasers calibration
system (D16)
Stabilized laser
Gauge Block
Interferometer
calibration system
Standard gauge
(D02)
Temperature、
pressure standard
Electricity
standard
Pressure
standard
block
Gauge block
Comparator
calibration system
(D01)
Gauge block
measurement
result
(Calibration certificate)
NML
resistance
temperature
detectors
calibration
system (T04)
NML the
fixed-point
calibration
system for
platinum
resistance
thermometers
(T05)
B970682
B970683
B980642
digital
thermometer
U = 0.029 ℃
4. competence
6. calibration intervals
NML twopressure
humidity
generator
calibration
system
(H01)
C970446
platinum
resistance
thermometer
Ga melting point：
NML direct
resistance
calibration
system
(E13)
NML gas
lubricated
piston gauge
calibration
System
(P04)
A980021
dew point
hygrometer
standard
resistor
U = 0.20 ℃
U = 20 µ
C970374
digital pressure
gage
U = 0.010 kPa
 TheUlaboratories
operating calibrations of
relevant
= 0.40 mK
auxiliary
parameters
are all inner labs of NML and
The triple point
of
water：U = 0.21 by
mK TAF.
accredited
 Calibration intervals indicate on their calibration
17
certificates issued by the laboratories.
Metrological traceability of gauge block measurement
- Complementary illustration in
documentation
SI unit
length (m)
MeP Fequency Stabilized laser,
fr , (Iodine stabilized He-Ne laser )
Frequency Stabilized
Lasers calibration
system (D16)
Fequency stabilized laser,
f λ, wavelength：
632.990 904 4 nm Gauge Block
Interferometer
calibration system
(D02)
Standard gauge block, Lr Deviation, d
2
0.5 mm to 100 mm
(mm)
Gauge block, LX
0.5 mm to 100 mm
2.
Comparator
calibration system
(D01)
Measured
difference, d1
(mm)
Gauge block
measurement
uncertainty
of measurement
result
3. documentation
Document No.
Expanded uncertainty
ICT:07-3-85-0051
MSVP:07-3-85-0033
20 kHz
ICT:07-3-93-0141
MSVP:07-3-93-0132
20 nm to 33 nm
ICT:07-3-86-0034
MSVP:07-3-86-0028
28 nm to 57 nm
Note:
Calibration Technique, ICT:
1. It Instrument
shows
complementary
illustration including
documented calibration procedure used in NML
uncertainties
2.documented
Measurementexpanded
System Validation
Procedure, MSVP:
calibration system
evaluation reportICT
usedand
in NML,
within
associated
with documented
MSVP
claimed uncertainty
recorded
18
in which
eachthe
traceability
step atisNML.
Discussion & Conclusion
19
Discussion & Conclusion
• Through the study activities for drawing metrological
traceability diagrams combined with mathematical
description, we will assure ourselves on knowledge
transfer of gauge block and the other measurement
systems with sufficient metrological know-how at NML.
• Since “reference to the SI units” is one of metrological
traceability elements, derived quantity would be more
complex than base quantity.
• We will keep elaborating to further and deepen the
concept of unbroken chain in metrological traceability
to every measurement system of any kind quantities
operating at NML.
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~The End~
Thanks for your attention
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