General presentation
Calibration and verification of thermometers. General information and description of the instruments

The unit of thermodynamic temperature, a fundamental physical quantity, is the kelvin (symbol K). The kelvin is one of the seven base units of the International System of Units (SI).

The kelvin is defined as the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. The term "degree Kelvin" should not be used.

Given the considerable progress made in recent years in redetermining Boltzmann's constant k_B, the kelvin will no doubt see its definition modified in the near future to link it to this fundamental constant.

For historical reasons, it is still common practice to express temperature in degrees Celsius (symbol °C). The Celsius temperature unit is equal to the kelvin unit by definition. A temperature difference or interval...