The kelvin, symbol K, is the SI unit of thermodynamic temperature. It is defined by taking the fixed numerical value of the Boltzmann constant k to be 1.380 649 x 10–23 when expressed in the unit J K–1, which is equal to kg m2 s–2 K–1, where the kilogram, metre and second are defined in terms of h, c and ΔνCs.
The Estonian National Standard Laboratory for Temperature realizes temperature scale
in measuring range (-38.8344 to +419.527) °C, using six temperature fixed-point cells (Hg, H20, Ga, In, Sn and Zn)
and a group of standard platinum resistance thermometers with two Precision Thermometry Bridges.
Calibration of thermometers is based on international temperature scale of ITS-90 in the
temperature range of (-196 to +420) °C with the expanded uncertainty of (1 to 80) mK.
Kristjan Tammik
kristjan.tammik@metrosert.ee