Measurement standard of temperature

DEFINITION

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 1.380 649×10–23 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 ∆νCs.

REALISATION OF THE SCALE

In the Estonian national temperature measurement standard laboratory the scale is realised in the measuring range (‑38.8344…+419.527) °C by using five temperature fixed points (Hg, H20, Ga, Sn and Zn) and a set of reference platinum resistance thermometers with a precision thermometry bridge. See the approved list of national measurement standards.

Water triple point cell at temperature +0.01°C

DEVICES AND POSSIBILITIES

For offering calibration services temperature fixed points, reference thermometers Isotech SPRT – 670SH and Hart Scientific 5682, thermostats Hart Scientific 7012, Hart Scientific 7341 and Isotech 915 and precision thermometry bridges ASL F700B and MI6010 are used.

Thermometers are calibrated pursuant to the international temperature scale ITS-90 in the temperature range (-80…+420) °C with expanded uncertainty of (1…160) mK.

 

ADDITIONAL INFORMATION

Kristjan Tammik
Phone +372 520 9495
E-mail kristjan.tammik@metrosert.ee