RTD (Resistance Temperature Detector)

The RTD (Resistance Temperature Detector) , also called resistance thermometer, is a temperature sensor that exploits the predictable change in electrical resistance of some materials with changing temperature. Resistance is measured by applying a constant current and measuring the voltage drop across the resistor. Ohm’s Law defines the proportionality between the resistance and the voltage. Therefore the voltage is a direct measure for the resistance and thereby the temperature. That means, when using resistors (RTD's) for temperature measurements, the electrical resistance of a sensor subjected to the temperature is the variable utilized.