Structure

Temperature Standard Laboratory

The head of the laboratory – Dr. Lilijana Gaidamovičiūtė
phone: +370 5 2502826

The mission of the Temperature Standard Laboratory (TSL) is the following:

  • to conduct scientific research in the field of thermometry;
  • to realize the unit of temperature, the kelvin, and the International temperature scale ITS-90 in the temperature range from 84 K (-189°C) to 1358 K (1085°C) and to disseminate them to lower-level standards;
  • to maintain the traceability of the magnitudes realized to the International system of units SI and to take part in the international comparisons of equivalence of the standards;
  • to provide the subjects of Lithuanian economy with the assistance from an open access centre in the field of thermometry, to foster the competitive ability of the business.
  • to ensure the traceability of measurement instruments belonging to the subjects of Lithuanian economy and being used for legal metrology to the primary standard. 

Operating principles of the standard

The standard realizes the unit of temperature and the International temperature scale ITS-90, which defines the international temperature of Kelvin (the symbol is T90) and the international temperature of Celsius (its symbol is t90). ITS-90 comprises the range from 0.65 K up to the highest temperature measurable in practice and expressed by the law of M. Planck.
 
The kelvin is a unit of a fundamental physical magnitude known as the thermodynamic temperature (the symbol is T), which is equal to the 1/273.16 part of the thermodynamic temperature of the water triple point. The kelvin is denoted by the letter K. To express the temperature with respect to the ice melting point (273.15 K), the temperature scale of Celsius is used (its symbol is t). The degree of Celsius is denoted by oC; it is equivalent to the kelvin by its magnitude.
 
The Lithuanian national standard of the unit of temperature is a primary standard. Its structure corresponds to the recommendations of the official description of ITS-90 (The International Temperature Scale of 1990 (ITS-90), BIPM, 1990). According to them, in the temperature range from the hydrogen triple point, 13.8033 K (-259.3467°C), to the freezing point of silver, 1234.93 K (961.78°C), the scale is realized by using the characteristic temperatures of the phase transitions in pure substances, at which a platinum resistance thermometer is calibrated. Continuous scale is realized by calculating the value of temperature from the resistance measured by using interpolation formulas based upon the resistance values at the characteristic (reference) points.