Unit of thermodynamic temperature: kelvin (K)
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.
Information on the practical realisation of the definition of the kelvin can be found in the Mise en pratique for the definition of the kelvin in the SI.
Humidity is the amount of water vapor present in the air (or any other gas). There are three main ways the express humidity: relative, absolute and and specific of which relative humidity is the most commonly used.
- Relative humidity is the amount of water vapor in the air, expressed as a percentage of the maximum amount that the air could hold at the given temperature; the ratio of the actual water vapor pressure to the saturation vapor pressure.
- Absolute humidity is the total mass of water vapor present in a given volume (g/m3) or mass of air (g/kg).
- Specific humidity (or moisture content) is the ratio of the mass of water vapor to the total mass of the moist air parcel.
Temperature and humidity calibration services