Practical Interpretation of Unbroken Chain in Metrological Traceability as to VIM 3

1. 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)

2. Outline • Introduction • Definition of “Metrological traceability” in VIM 3 • Typical Metrological Traceability Diagram • Additional Mathematical Description • Case study - Gauge Block Measurement • 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 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

5. Introduction • National Measurement Laboratory (NML, the NMI inTaiwan) 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.

6. Definition of “Metrological traceability” in VIM 3

7. 2007 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.

8. Reference Measurement standard Measurement procedure Measurement unit 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. Metrological traceability Unbroken chain of calibrations Calibration document Calibration Measurand document Calibration Measurement Result document Measurement result Measurement uncertainty Measured quantity value &

9. 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.

10. Typical metrological traceability diagram

11. Typicalmetrological traceability diagram • Hardness traceability chainin Metrologia 47(2010) S59–S66 (Traceability in hardness measurements: from the definition to industry)

12. Typicalapproach of NML’s metrological Traceability Diagram • Measurement System Validation Procedure (MSVP). • The traceability illustration in figures cannot fully cover the aforementioned six important elements of metrological traceability. • For a specific measured quantity of calibration at NML, there will be two documents: • Instrument Calibration Technique (ICT) • Measurement System Validation Procedure (MSVP). Gauge block comparator measurement traceability diagram Mass measurement system traceability diagram

13. Additional MathematicalDescription

14. 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

16. Metrological traceability of gauge block measurement SI unit length (m) SI unit : length (m) MeP FequencyStabilized laser, fr , (Iodine stabilized He-Ne laser ) Frequency Stabilized Lasers calibration system Fequency stabilized laser, fλ, wavelength： 632.990 904 4 nm Frequency deviation, △f (kHz) Gauge Block Interferometer calibration system Standard gauge block, Lr 0.5 mm to 100 mm Deviation, d2(mm) Gauge Block Comparator calibration system Gauge block, LX 0.5 mm to 100 mm Measured difference, d1(mm)  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. Gauge block measurement result 1. an unbroken chain 5. reference to SI units

17. Metrological traceability of auxiliary parameters SI unit length (m) SI units K  Pa K K Pa MeP Stabilized laser Frequency Stabilized Lasers calibration system (D16) Stabilized laser Temperature standard Temperature standard Electricity standard Temperature、 pressure standard Pressure standard Gauge BlockInterferometer calibration system (D02) Standard gauge block Comparator calibration system (D01) Gauge block NMLthe fixed-point calibration system for platinum resistance thermometers (T05) NML two- pressure humidity generatorcalibration system (H01) NMLresistance temperature detectors calibration system (T04) NML gas lubricated piston gaugecalibrationSystem (P04) NML direct resistance calibration system (E13) Gauge block measurement result B970682 B970683 B980642 C970446 A980021 C970374 (Calibration certificate) digital thermometer platinum resistance thermometer dew point hygrometer standard resistor digital pressure gage Ga melting point： U = 0.40 mK U = 0.20 ℃ U = 20 µ U = 0.010 kPa U = 0.029 ℃  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. The triple point of water：U = 0.21 mK 4. competence 6. calibration intervals

18. Metrological traceability of gauge block measurement- Complementary illustration in documentation SI unit length (m) MeP FequencyStabilized laser, fr , (Iodine stabilized He-Ne laser ) Document No. Expanded uncertainty Frequency Stabilized Lasers calibration system (D16) ICT:07-3-85-0051 MSVP:07-3-85-0033 20 kHz Fequency stabilized laser, fλ, wavelength： 632.990 904 4 nm Gauge Block Interferometer calibration system (D02) ICT:07-3-93-0141 MSVP:07-3-93-0132 20 nm to 33 nm Standard gauge block, Lr 0.5 mm to 100 mm Deviation, d2 (mm) Comparator calibration system (D01) ICT:07-3-86-0034 MSVP:07-3-86-0028 28 nm to 57nm Gauge block, LX 0.5 mm to 100 mm Measured difference, d1 (mm) • Note: • Instrument Calibration Technique, ICT: • documented calibration procedure used in NML • Measurement System Validation Procedure, MSVP: calibration system evaluation report used in NML, within which the claimed uncertainty is recorded  It shows complementary illustration including documented expanded uncertainties associated with documented ICT and MSVP in each traceability step at NML. Gauge block measurement result 2. uncertainty of measurement 3. documentation

19. Discussion & Conclusion

20. 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 chainin metrological traceability to every measurement system of any kind quantities operating at NML.

21. ~The End~ Thanks for your attention