The principle of temperature measurement is based on the characteristic that the resistance value of a conductor or semiconductor changes with temperature. It also has many advantages, such as remote transmission of electrical signals, high sensitivity, strong stability, good interchangeability and accuracy. However, it requires power excitation and cannot measure temperature changes instantaneously. Different conductors have different electron densities, which result in certain electron diffusion. When they reach a certain equilibrium, the potential formed depends on the material properties of the two different conductors and the temperature at their contact point.

The wear-resistant thermistor adopts a three wire system to eliminate measurement errors caused by the resistance of the connecting wires. This is because the circuit for measuring thermal resistance is usually an unbalanced bridge. As a bridge arm resistor of the electric bridge, the thermal resistor's connecting wire (from the thermal resistor to the central control room) also becomes a part of the bridge arm resistor. This part of the resistor is unknown and varies with the ambient temperature, causing measurement errors. Adopting a three wire system, one wire is connected to the power terminal of the bridge, and the other two wires are respectively connected to the bridge arm where the thermal resistance is located and the adjacent bridge arm, thus eliminating measurement errors caused by the resistance of the wire line.