A black body is a body on which no reflection or transmission occurs. Incident electromagnetic radiation of any wavelength is completely absorbed by the black body.

This makes the black body ideal for understanding the physical principles of non-contact temperature measurement technology and for calibrating and adjusting pyrometers, infrared thermometers and infrared temperature sensors. A black body radiator has an angle-independent radiation density and emits the maximum possible energy at every wavelength.

The intensity and frequency distribution of the electromagnetic radiation emitted by a black body are described by Planck’s law of radiation (according to Max Planck).

An ideal black body cannot be realised. There are no known materials that completely absorb electromagnetic waves regardless of frequency. A carbonised surface has an absorption coefficient of approx. 0.96-0.98 in the visible spectral range, but not at other wavelengths.

In practice, blackbody calibrators are used to adjust and calibrate pyrometers, infrared thermometers and infrared temperature sensors.

A reference temperature is set on the blackbody calibrator, e.g. 100°C, and the pyrometer is adjusted until it also displays 100°C.