Temperature Transmitters

An RTD (resistance temperature detector) is a temperature sensor that works on the principle that the resistance of a conductor changes with temperature.

Discovered and put into use after the thermocouple, resistance thermometers are now very widely used in industry and in laboratories.

The wound resistance element is immersed in the medium whose temperature is to be measured and a constant current is passed through it. As the temperature changes, the resistance changes, and the constant current produces a varying voltage that is read as the measurement.