Any instrument used for measuring high temperatures by means of the thermal radiation emitted by a hot object. In a radiation pyrometer the emitted radiation is detected by a sensor such as a thermocouple. In an optical pyrometer the colour of an electrically heated filament is matched visually to that of the emitted radiation. Pyrometers are especially useful for measuring the temperature of distant, moving, or inaccessible objects.
Subjects: Astronomy and Astrophysics.