Thermal resistance is one of the most commonly used temperature measuring elements in low and medium temperature region. Generally, thermocouples are used to measure higher temperatures above 500 C. However, in the low and medium temperature region below 500 C, because of its small output thermoelectric potential, the anti-interference method for the secondary appearance is highly demanded. If thermocouples are selected, it is generally difficult to achieve accurate measurement.

Therefore, in the lower temperature region, considering the relative error caused by the change of the cold end temperature, it is generally appropriate to use thermal resistance temperature to measure the appearance. This is because the thermal resistance in the middle and low temperature region has the characteristics of high measurement accuracy and stable function. The measuring principle of thermal resistance is based on conductor or semiconductor. There is a functional relationship between the resistance of data and temperature.

That is, when the temperature changes, the resistance of the conductor or or semiconductor will also change, and then the temperature value of the target will be displayed through the appearance. Thermal resistance is mostly made of pure metal materials, and now the most widely used thermal resistance data are platinum and copper. Platinum resistance has high accuracy and is suitable for neutral and oxidizing media. It has good stability and non-linearity. The higher the temperature, the smaller the change rate of resistance.

Copper resistance is linearly related to temperature in the range of temperature measurement. It is suitable for non-corrosive media. In addition, the materials of nickel, manganese and rhodium are also used to make thermal resistance. The composition and cohesion of the thermal resistance temperature measurement system are as follows: the composition of the thermal resistance temperature measurement system. The thermal resistance temperature measurement system is generally composed of thermal resistance, cohesive conductor and appearance.