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Stabilization of SPRTs for ITS-90 Calibrations



Dennis B. Minor, Gregory F. Strouse


At the National Institute of Standards and Technology (NIST), the ITS-90 calibration of standard platinum resistance thermometers (SPRTs) is performed in the Platinum Resistance Thermometer Calibration Laboratory over the temperature range from -189 C to 962 C. As part of the quality system internal measurement assurance program, the stabilization of the SPRT prior to calibration is used to determine when and if the thermometer is stable enough to be calibrated within the NIST-assigned ITS-90 realization uncertainties. The resistance of the SPRT at the triple point of water, R(TPW), must repeat after a stabilization cycle to within the equivalent of 0.2 mK within five stabilization cycles to qualify for calibration. The annealing procedure depends on the calibration temperature range and the amount of change at the TPW between the as received value and the previous NIST calibration value. The stabilization techniques used and the impact on the overall stability of the SPRT during a calibration are given.
Conference Dates
August 7-11, 2005
Conference Title
NCSLI Conference


Anneal, calibration, ITS-90, quality assurance, SPRT


Minor, D. and Strouse, G. (2005), Stabilization of SPRTs for ITS-90 Calibrations, NCSLI Conference (Accessed June 16, 2024)


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Created August 1, 2005, Updated February 17, 2017