Every body emits electromagnetic radiation above absolute zero (-273.15°C). There is a fixed relationship between the emitted radiation and the temperature of the body.

In non-contact temperature measurement, the thermal radiation emitted by an object in the infrared range is measured by a pyrometer and converted into a measurement signal (analogue or digital).
The thermal radiation from the measurement object is picked up by the optics of the infrared temperature sensor and converted into an electrical measurement signal and linearised by the sensor’s internal electronics.

This standardised measurement signal can be further processed, e.g. in a PLC, LED display, PIB controller or a panel meter.