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Present Estimates of the Differences Between Thermodynamic Temperatures and the ITS-90



Joachim Fischer, M. DePodesta, K. D. Hill, Michael R. Moldover, Laurent Pitre, R. Rusby, Peter Steur, Osamu Tamura, R. White, L. Wolber


In 2005, the Consultative Committee for Thermometry (CCT) recommended the creation of a Mise en pratique for the definition of the kelvin and envisioned that future versions of the Mise en pratique would recommend values of the differences between thermodynamic temperatures and ITS-90 temperatures (T − T90). At the CCT's request, Working Group 4 (WG4) critically reviewed all available measurements of T − T90, the uncertainties, and documented the conversion of older data to the ITS-90. From the review, we provide consensus estimates of T - T90 for selected measurements from 4.2 K to 1358 K as well as a recommendation for T − T90 spanning the range 0.65 K to 4.2 K. WG4 identified certain temperature ranges where researchers are encouraged to undertake additional high-accuracy measurements of T - T90. In order to disseminate the differences T - T90 via the Mise en pratique, we provide two analytic functions for T - T90, one for use below TTPW and one for use above TTPW. The discontinuity of the derivative dT90/dT at TTPW is discussed and the consistency with the results of recent acoustic gas thermometry and with the resistance ratios of platinum resistance thermometers is investigated.
Proceedings Title
Conference Dates
May 31-June 4, 2010
Conference Location
Portorož, SI
Conference Title
Joint International Symposium on Temperature, Humidity, Moisture and Thermal Measurements in Industry and Science


differences, T – T90, International Temperature Scale ITS-90, primary thermometry, thermodynamic temperature


Fischer, J. , DePodesta, M. , Hill, K. , Moldover, M. , Pitre, L. , Rusby, R. , Steur, P. , Tamura, O. , White, R. and Wolber, L. (2011), Present Estimates of the Differences Between Thermodynamic Temperatures and the ITS-90, 2010 TEMPMEKO & ISHM, Portorož, SI, [online], (Accessed June 22, 2024)


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Created January 28, 2011, Updated October 12, 2021