Instrumentation and control requirements for deployment of modular ...
Inter-Laboratory Comparison Study Using Modular Instrumentation and Lessons Learned
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Transcript of Inter-Laboratory Comparison Study Using Modular Instrumentation and Lessons Learned
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Inter-Laboratory Comparison Study Using Modular
Instrumentation and Lessons Learned
Author: Dimaries Nieves – National InstrumentsSenior Metrology Engineer
Speaker: Jorge Martins – National InstrumentsPrincipal Metrology Engineer
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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.
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• 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
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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.
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NI Inter-Laboratory Comparison Proposal• The ILC was designed based on:
• NCSLI’s RP-15 • ASTM E691-13
• Unit was monitored using the petal or flower model
• NI Certified Calibration Centers were selected to participate
• NIC Metrology Laboratory serves as the pivot Laboratory
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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.
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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.
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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).
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For Evaluation
An En value was calculated for each measurement provided for each laboratory
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Resistance Measurement Verification in 2-wire mode First ILC (2011)
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Resistance Measurement Verification in 4-wire mode
First ILC (2011)
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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).
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Resistance Measurement Verification in 2-wire mode Second ILC (2012)
Pivot
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Resistance Measurement Verification in four-wire mode Second ILC (2012)
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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
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Additional Analysis• Consistency Evaluation
• Between Laboratory
• Where, = Lab average minus the average of the lab averages
• Where, Sx = Standard deviation of the lab averages
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Within-laboratory consistency (k) for DC Voltage measurement Second ILC (2012)
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Between-laboratory consistency (h) for DC Voltage measurement
Second ILC (2012)
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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
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Questions?