Development of absolute acoustic gas thermometer for the state primary standard of the temperature unit – kelvin in the range 0.3-273.16 K in VNIIFTRI and the total standard uncertainty of the thermodynamic temperature measurements near the triple point of water

Spotlight on Luminescence Thermometry: Basics, Challenges, and Cutting‐Edge Applications

“…Aside from the differences outlined above in the working principle, luminescent thermometers can be further divided into primary and secondary categories based on the thermodynamic laws and variables used to determine temperature. Whereas secondary thermometers require a calibration procedure to determine the relationship between the observed changes in a thermometric parameter and the temperature, the primary ones allow the absolute determination of the temperature using state equations, such as those for ideal gases, [ 5,347 ] thermal noise in electrical resistors, [ 348 ] speed of sound in a gas, [ 349 ] Doppler broadening of an optical transition, [ 350 ] and black body radiation. [ 351 ] On the other hand, the metrologist perspective on primary thermometers, framed by the current redefinition of the temperature using the Boltzmann constant, defines a primary thermometer as an instrument that presents a well‐understood connection between a measurable quantity (thermometric parameter) and k B T , [ 5 ] the average energy per degree of freedom.…”