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ITS-90 SPRT Calibration from the Ar TP to the Zn FP



Michal J. Chojnacky, Tobias Herman, Ken Hill, Steffen Rudtsch, Inseok Yang, Petrus Paulus Maria Steur, Roberto Dematteis, Lopardo Lopardo, Fernando Sparasci, Catherine Martin, Lara Risegari, Januarius Widiatmo, Tohru Nakano, Ikuhiko Saito, Klaus Natorf Quelhas, Patricia Giorgio, Jianping Sun, Jintao Zhang, Jonathan Pearce, Jayne Gray


This is a report to the Consultative Committee for Thermometry (CCT) on the key comparison 9 of SPRT calibration on the International Temperature Scale of 1990 (ITS-90) from 83.8058 K (the Ar triple point) to 692.677 K (the Zn freeze point). The comparison followed a collapsed star protocol, with each of the fourteen participating laboratories shipping two standard platinum resistance thermometers (SPRTs) as transfer standards to the pilot laboratory (National Institute of Standards and Technology, NIST) for a direct comparison of SPRT calibration at the National Metrology Institute (NMI) of origin to calibration at NIST. Measurements were taken at the participating laboratories before and after measurement at NIST to asses the effect of transportation on the transfer standards. The pooled results from all laboratories were combined to calculate a key comparison reference value (KCRV). This report includes the calculation of, and comparisons to, the KCRV as well as bilateral comparisons between labs. In addition, there is space devoted to analysis of the scatter in shifts in SPRT values following travel.


temperature metrology, key comparison


Chojnacky, M. , Herman, T. , Hill, K. , Rudtsch, S. , Yang, I. , Steur, P. , Dematteis, R. , Lopardo, L. , Sparasci, F. , Martin, C. , Risegari, L. , Widiatmo, J. , Nakano, T. , Saito, I. , Quelhas, K. , Giorgio, P. , Sun, J. , Zhang, J. , Pearce, J. and Gray, J. (2023), ITS-90 SPRT Calibration from the Ar TP to the Zn FP, BIPM, [online],,, (Accessed June 15, 2024)


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Created March 30, 2023, Updated December 21, 2023