The article describes the composition and metrological characteristics of the State Primary Standard of temperature unit – kelvin – in the range from 0.3 K to 273.16 K GET 35-2021. GET 35-2021 allows reproducing and disseminating the temperature unit in accordance with the definition of kelvin, accepted at the 26th General Conference on Weights and Measures (26th CGPM) in 2018. GET 35-2021 includes three installations of acoustic gas thermometry developed in 2012–2019, which are the primary means of measuring temperature in the ranges of 79–273.16 K, 4.2–80K, 268.16–273.16 K. Equipment for reproducing the reference points of the International Temperature Scale ITS-90 has been upgraded in order to improve the accuracy. Based on the studies performed, the uncertainty of reproducing the thermodynamic temperature and temperature according to ITS-90 has been calculated.
Description and metrological characteristics are presented of upgraded in 2021 equipment of National primary state standard of temperature on the temperature range from 0.3 K to 273.16 K GET 35-2021. GET 35-2021 allow to to the reproduce and disseminate the unit of temperature according to its definition accepted on 26th CGPM in 2018. Three installations of acoustic gas thermometry developed in 2012–2019 have been introduced in the National primary state standard covering ranges 79–273.16 K, 4.2–80 K, 268.16–273.16 K. The equipment for reproduction of fixed points of of International Temperature scale ITS-90 has been upgraded for uncertainty reduction. Uncertainty of reproduction of thermodynamic temperature and temperature according to ITS-90 have been calculated on the basis of investigations of upgraded equipment.
Systems for realizing the fixed points of the ITS-90 for calibrating column and capsule standard platinum thermometers, namely, the triple points of argon and mercury and the melting point of gallium, are constructed and investigated. The errors of the values of the metrological characteristics of the systems obtained enable one, using platinum resistance thermometers, to reproduce and transfer the temperature scale in the 83.8–302.9 K range. The extended uncertainty in reproducing the temperatures of the fixed points does not exceed 0.4 mK.
A device for achieving the argon triple point for calibrating resistance thermometers is described. The device is a cryostat with sealed cells filled with pure argon. Tests have shown that the spread in values of the argon triple point is within +/-0.2 mK, and the total error of calibration of platinum thermometers is below 0.4 mK, providing the use of this device for calibrating long-stem and capsule platinum thermometers measuring temperature according to the ITS-90 scale with an error below 1.5 mK.
