Thermoresistors are detectors, commonly known as “RTD” – “Resistence Temperature Dependent” or calibrated resistance elements where their operation is based on the characteristic variation of resistance with temperature, essential to some materials, usually platinum, nickel or copper. Its application is broad in the various sectors of the technique of measurement and automation of temperature in the industries in general. Usually it is applied in installations of great responsibility as, for example, in very irregular intermittent regime. The same detector can be used for alarm and shutdown.

The most common RTDs are called “platinum” and “copper”, which has their resistances at 0ºC respectively of 100 and 10 Ohms. The use of RTD’s for engines, especially at the national level, has so far been made in greater numbers with the “platinum” or Pt100. They consist of a calibrated resistance, which has as a characteristic a linear dependence between the resistivity of the sensor material and the temperature at which it is subjected. This allows continuous monitoring of the motor heating process through the controller display, with a high degree of precision and accuracy of response.