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Proficiency Testing for Achieving Accreditation in Thermometry

Published

Author(s)

Sally S. Bruce, Gregory F. Strouse

Abstract

The establishment of traceability is an essential component of laboratory accreditation for Calibration laboratories accredited by the National Voluntary Laboratory Accreditation Program (NVLAP). Traceability requires that an unbroken chain of comparisons to national standards with stated and documented uncertainties be established. The use of proficiency testing is an important tool for validating uncertainty claims contained within a Scope of Accreditation. As such, the National Institute of Standards and Technology (NIST) Thermometry Group conducts proficiency testing for NVLAP accredited contact thermometry laboratories. These proficiency tests include: thermometric fixed points, standard platinum resistance thermometers, industrial platinum resistance thermometers, thermistors, thermocouples, and liquid-in-glass thermometers. The NIST Thermometry Group proficiency tests scale inversely in difficulty as a function of the uncertainties contained within a facility s Scope of Accreditation. The offered proficiency tests are designed to establish confidence in the participant s calibration capabilities and uncertainty claims without being an undue burden to the calibration facility. The NIST Thermometry Group proficiency tests involve measurements of NIST-owned artifact(s) at NIST, measurements of the artifact(s) at the participant s calibration facility, and then a second set of measurements at NIST. On completion of the measurement phase of a proficiency test, a detailed report is generated to give the difference in temperature realization between that of the participant and NIST and the degree of equivalence. For each test point, an En value (degree of equivalence) is calculated by , where UC is the combined expanded uncertainty of the participant and NIST. An value of less than one signifies compliance for the participant. As part of the goal to improve the participant s measurement capabilities, the report also gives suggested solutions to any identified measurement issues that need attention.The role of proficiency testing as part of the process in achieving NIST National Voluntary Laboratory Accreditation Program (NVLAP) accreditation in thermometry is discussed in the paper. Additionally, the descriptions of the NIST Thermometry Group unbiased third-party proficiency tests and some unidentified participant results are given.
Citation
International Journal of Thermophysics

Keywords

Accrediation Program, ITS-90, National Voluntary Laboratory, NVLAP, proficiency test, Scope of Accreditation, temperature, thermometry, traceability
Created June 5, 2008, Updated June 27, 2017