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Transcript of 1 Practical Interpretation of Unbroken Chain in Metrological Traceability as to VIM 3 Center for...
1
Practical Interpretation of Unbroken Chain in Metrological Traceability
as to VIM 3
Center for Measurement Standards (CMS)Industrial Technology Research Institute
(ITRI)
Authors: Yi-Ting Chen, Lung-Hen Chow, Liang-Hsing Chen, and Gwo-Sheng Peng
2
Outline
1. Introduction
2. Definition of “Metrological traceability” in VIM 3
3. Typical Metrological Traceability Diagram
4. Additional Mathematical Description
5. Case study - Gauge Block Measurement
6. Discussion and Conclusion
3
Introduction
4
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 whic
h can be related to a reference – an evidence of measurands tracing to the primary standar
ds which can realize the SI units
– a documented unbroken chain of calibrations
5
Introduction• National Measurement Laboratory (NML, the NMI
in Taiwan) has operated its mission since 1987. Effective knowledge transfer has become an essential issue.
• Gauge block measurement is demonstrated for such purpose at NML.
• In dealing with definition of “metrological traceability” in VIM 3, additional mathematical description is taken to enhance the practical interpretation of the definition.
6
Definition of “Metrological traceability” in VIM 3
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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
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Metrological traceabilityProperty 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.
Unbroken chain of calibrations
Metrological traceability
Metrological traceability
Measurement result
Calibration
Calibration
CalibrationMeasurement
Result
Measurand
Reference
Measurement standard
Measurement procedure
Measurement unit
Measurement uncertainty
Measured quantity value&
document
document
document
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Six important elements in ILAC P-10
1. an unbroken chain2. uncertainty of measurement3. documentation4. competence5. reference to SI units6. calibration intervals
The International Laboratory Accreditation Cooperation (ILAC) also proposed six important elements to confirm the definition of “metrological traceability” :
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.
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Typical metrological traceability diagram
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Typical metrological traceability diagram• Hardness traceability chain in Metrologia 47(2010) S59–S66
(Traceability in hardness measurements: from the definition to industry)
12
• For a specific measured quantity of calibration at NML, there will be two documents: – Instrument Calibration Technique (ICT)– Measurement System Validation Procedure
(MSVP).
Typical approach of NML’s metrological Traceability Diagram
Gauge block comparator measurement traceability diagram
Mass measurement system traceability diagram
• Measurement System Validation Procedure (MSVP).• The traceability illustration in figures cannot fully cover the
aforementioned six important elements of metrological traceability.
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Additional MathematicalDescription
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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.
15
Case study - Gauge Block Measurement
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Gauge Block Comparator
calibration system
Metrological traceability of gauge block measurement
ncalculatio fromnumber stripe ceinterferen:tmeasuremen fromnumber stripe ceinterferen:
h wavelengtumlaser vacu:eterinterferomblock gauge from deviation:
(3) )(2
2
2
d
d
SI unitlength (m)
Gauge Block Interferometer calibratio
n system
Frequency Stabilized Lasers calibration
systemFequency stabilized laser,
f λ, wavelength:632.990 904 4 nm
Standard gauge block, Lr
0.5 mm to 100 mm
Gauge blockmeasurement
result
Gauge blockmeasurement
result
Measured difference, d1 (m)
Gauge block, LX
0.5 mm to 100 mmcomparatorblock gauge from differencet measuremen
block gauge standard ofresult t measuremen block gauge calibrated ofresult t measuremen
(1)
r
x
x
:::
dLL
dLL r
1
1
eterinterferom block gauge from deviation comparator block gauge from difference mesurement
block gauge standard of value nominal block gauge calibrated of result tmeasuremen x
x
::::
2
1
N
21N
ddLL
ddLL
eterinterferomblock gauge from deviation block gauge standard of valuenominal
block gauge standard ofresult t measuremen (2)
2
r
2r
:::
dLL
dLL
N
N Deviation, d2 (m)
The left-hand parameter of the equation is unknown and the right-hand parameters are known. In mathematical approach, an unbroken chain is demonstrated and measurement result of each step traced to the measurand of the previous step.
MeP Fequency Stabilized laser,fr , (Iodine stabilized He-Ne laser )
vacuuminlight of velocity cindex refractive n
tmeasuremenfrequency beat of deviationfrequency laser standard of valuefrequency laser calibrated of valuefrequency
(4) Δ , n
c
0
r
r0
:::::
f
ff
ffff
SI unit : length (m)
Frequency deviation, f △ (kHz)
1. an unbroken chain5. reference to SI units
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SI units
platinum resistance thermometer
dew point hygrometer
U = 0.20 ℃
B970682B970683
C970446
Metrological traceability of auxiliary parameters Metrological traceability of auxiliary parameters
NML the fixed-point calibration system for platinum
resistance thermometers
(T05)
NML two- pressure humidity
generator calibration
system (H01)
K K Pa
standard resistor
digital pressure gage
U = 20 µ U = 0.010 kPa
C970374A980021
Electricitystandard
NML gas lubricated
piston gauge calibration
System (P04)
NML direct resistance calibration
system (E13)
Pa
digital thermometer
U = 0.029 ℃
B980642
NML resistance
temperature detectors calibration syste
m (T04)
Temperaturestandard
KSI unit
length (m)
Gauge Block Interferometer calibratio
n system (D02)
Frequency Stabilized Lasers calibration
system (D16)
Comparator calibration system
(D01)
Standard gaugeblock
Stabilized laser
Gauge blockmeasurement
result
Gauge blockmeasurement
result
Gauge block
Temperaturestandard
Pressurestandard
Temperature、pressure standard
The triple point of water: U = 0.21 mK
Ga melting point: U = 0.40 mK The laboratories operating calibrations of relevant
auxiliary parameters are all inner labs of NML and accredited by TAF. Calibration intervals indicate on their calibration certificates issued by the laboratories.
MeP Stabilized laser
(Calibration certificate)
4. competence6. calibration intervals
18
20 kHz
Expanded uncertaintyDocument No.
20 nm to 33 nm
28 nm to 57 nmICT:07-3-86-0034MSVP:07-3-86-0028
ICT:07-3-93-0141 MSVP:07-3-93-0132
ICT:07-3-85-0051MSVP:07-3-85-0033
SI unitlength (m)
Gauge Block Interferometer calibratio
n system (D02)
Frequency Stabilized Lasers calibration
system (D16)
Comparator calibration system
(D01)
Fequency stabilized laser,f λ, wavelength:
632.990 904 4 nm
Standard gauge block, Lr
0.5 mm to 100 mm
Gauge blockmeasurement
result
Gauge blockmeasurement
result
Measured difference, d1
(m)
Gauge block, LX
0.5 mm to 100 mm
Deviation, d2
(m)
MeP Fequency Stabilized laser,fr , (Iodine stabilized He-Ne laser )
Note:1. Instrument Calibration Technique, ICT:
documented calibration procedure used in NML2. Measurement System Validation Procedure, MSVP:
calibration system evaluation report used in NML, within which the claimed uncertainty is recorded
Metrological traceability of gauge block measurement
- Complementary illustration in documentation
It shows complementary illustration including documented expanded uncertainties associated with documented ICT and MSVP in each traceability step at NML.
2. uncertainty of measurement3. documentation
19
Discussion & Conclusion
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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.
• 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.
• Since “reference to the SI units” is one of metrological traceability elements, derived quantity would be more complex than base quantity.
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Thanks for your attention
~The End~