Inter-Laboratory Comparison Study Using Modular Instrumentation and Lessons Learned

1. Inter-Laboratory Comparison Study Using Modular Instrumentation and Lessons Learned Author: Dimaries Nieves – National Instruments Senior Metrology Engineer Speaker: Jorge Martins – National Instruments Principal Metrology Engineer

2. Learning Objectives • How can we demonstrate performance and competence of modular instrumentation as part of metrology and accreditation process? • Propose a process to perform an Inter-laboratory Comparison using a modular instruments. • Standard Documents for ILC evaluation. • Review some of the results and lessons learned.

3. Inter-laboratory Comparison (ILC) is a key criterion for laboratory accreditation • ILC is an important asset in: • Measurement Reliability • Measurement Assurance • Calibration Process Confidence • Measurement Method • Technician Proficiency • There is no commercial proficiency testing available for Modular Instrumentation. For the last two years, National Instruments performed an interlaboratory comparison using Modular Instrumentation as the primary standard

4. Modular Instruments • Gradually taking an important role in test and measurement • Enable more cost effective and flexible measurements • Used in Research, Calibration, Validation and Production test • In metrology and laboratory accreditation process • Need to demonstrate performance and competence performing regular calibration services.

5. NI Inter-Laboratory Comparison Proposal • The ILC was designed based on: • NCSLI’s RP-15 • ASTM E691-13 • NIC Metrology Laboratory serves as the pivot Laboratory • Unit was monitored using the petal or flower model • NI Certified Calibration Centers were selected to participate

6. ILC Equipment Bias and Stability • Stability of the reference unit was determined by the pivot Laboratory before starting the ILC process. • No significant bias was found within the pivot measurements. • The pivot laboratory monitor the performance of the unit to ensure that any unexpected changes in the traveling standard are promptly detected. • Comparison of the pivot lab data showed that the unit remained in control throughout the all ILC.

7. ILC Reference Value • Reference values were determined using the pivot lab measurements. • All pivot runs were included in the analysis • Statistical Analysis of the data was performed • Uncertainties reported by the pivot laboratory include ILC process bias and deviations.

8. First ILC Run • NI PXI-4072 Flex DMM and LCR Meter (6 ½ digits DMM) • NI Published Calibration Procedure • “Verify Mode Only” procedure using NI’s calibration software, Calibration Executive • Participants use their own chassis, standards, and cables to perform the measurements • Report only one measurement result per point with an expanded uncertainty at 95% of confidence (k=2).

9. For Evaluation An En value was calculated for eachmeasurement provided for eachlaboratory

10. Resistance Measurement Verification in 2-wire mode First ILC (2011)

11. Resistance Measurement Verification in 4-wire mode First ILC (2011)

12. Second ILC Run • NI PXI-4072 FlexDMM and LCR Meter (6 ½ digits DMM) , Chassis and Cables (entire Setup). • NI Published Calibration Procedure • “Verify Mode Only” procedure using NI’s calibration software, Calibration Executive • Performed three runs on the unit, doing a manual “Self Calibration” before each run • Verify that the board temperature was stable at 35 ºC ± 2 ºC before performing the verification • Report measurement result with an expanded uncertainty at 95% of confidence (k=2).

13. Resistance Measurement Verification in 2-wire mode Second ILC (2012) Pivot

14. Resistance Measurement Verification in four-wire mode Second ILC (2012)

15. Additional Analysis • Consistency Evaluation • Within the laboratory • S = Standard Deviation for one laboratory • Sr = Repeatability standard deviation of the equipment • p = Number of laboratories participating in the ILC

16. Additional Analysis • Consistency Evaluation • Between Laboratory • Where, = Lab average minus the average of the lab averages • Where, Sx = Standard deviation of the lab averages

17. Within-laboratory consistency (k) for DC Voltage measurement Second ILC (2012)

18. Between-laboratory consistency (h) for DC Voltage measurement Second ILC (2012)

19. Conclusion • Modular Instruments meet the published measurement specifications, regardless of the combination of chassis, controller and measurement I/O. • However, for an ILC the higher requirements for repeatability and reproducibility make it advantageous to provide, not just the instrument but, the entire measurement system. • Including the entire system in the ILC reduces differences between participants, improving the correlation of data. • Several statistical tools are needed

20. Questions?