Thermal Characteristics of the NIST Fixed-Point Cells, Furnaces, and Maintenance Baths Over the Temperature Range From 83.8058 K to 1234.93 K
Gregory F. Strouse, G T. Furukawa
The optimal realization of an International Temperature Scale of 1990 (ITS-90) defining fixed-point temperature, for accurate calibration of the (high-temperature) standard platinum resistance thermometer [(HT) SPRT], critically depends on the thermal characteristics of the furnace or maintenance bath, the design of the fixed-point cell assembly, and the thermal contact of the (HT) SPRT with the liquid/solid interface of the fixed-point substance of the highest purity (>99.9999% pure). At NIST, several different types of furnaces and maintenance baths are used to realize the nine ITS-90 fixed points which cover the temperature range from 83.8058 K to 1234.93 K. The furnaces, maintenance baths, and fixed-point cells are designed to minimize the temperature difference over the length of the fixed-point cell crucibles during fixed-point realization to less than 10 mK. Additionally, to insure that the (HT) SPRT is properly measuring the fixed-point cell temperature, the fixed-point assemblies are designed such that the furnace or maintenance bath increases the immersion of the (HT) SPRT in the re-entrant well of the fixed- point cell.
TEMPMEKO '99, the 7th International Symposium on Temperature and Thermal Measurements in Industry and Science
June 1-3, 1999
International Symposium on Temperature and Thermal Measurements
and Furukawa, G.
Thermal Characteristics of the NIST Fixed-Point Cells, Furnaces, and Maintenance Baths Over the Temperature Range From 83.8058 K to 1234.93 K, TEMPMEKO '99, the 7th International Symposium on Temperature and Thermal Measurements in Industry and Science, Delft, NL, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=830624
(Accessed November 29, 2023)