A radiometer is a device used to measure the radiant flux or power in electromagnetic radiation. Although the term is perhaps most generally applied to a device which measures infrared radiation, it can also be applied to detectors operating any wavelength in the electromagnetic spectrum.

The radiation detector within a radiometer is most often a bolometer which absorbs the radiation falling on it and as a result rises in temperature which can be measured by a thermometer of some type. This temperature rise can be related to the power in the incident radiation.

An early detector of infrared and visible radiation (light) was the Crookes radiometer.

Measuring instruments | Radiometry

Radiometer | Radiomètre | Радиометр | Radiometri