The structure of the high and low temperature box can be roughly divided into six parts: automatic control system, refrigeration system, heating system, environmental humidity automatic control system, I sensor system, and gas circulation system (the high and low temperature box has no environmental humidity automatic control system). What is the principle and operation mode of the main system of the high and low temperature box discussed by the editor and everyone?

1. Automatic control system:

The automatic control system is the main part of the high and low temperature box. It determines the temperature raising speed of the test box, the precision, and whether there is a system control. A tuning method composed of PID and controller design.

2. Refrigeration system:

The refrigeration system is one of the core parts of the high and low temperature box. The refrigeration methods of the test box can usually be divided into two types: mechanical equipment refrigeration and liquid oxygen auxiliary refrigeration. Mechanical equipment refrigeration is the use of vapor reduction refrigeration, and they are mainly composed of refrigeration compressors. Coolers .The throttle valve device and the air conditioner evaporator are composed. Because the ultra-low temperature of the test should be -55 degrees Celsius, the unipolar refrigeration cannot meet the requirements. Therefore, the refrigeration method of the comprehensive test box generally adopts the cascade refrigeration. Liquid oxygen refrigeration It mainly uses the basic principle of digesting and absorbing a lot of calories when liquid oxygen changes from liquid to vapor state to complete rapid cooling. In the whole process of specific application, liquid oxygen refrigeration is usually used as a refrigeration supplement for refrigeration compressors and mechanical equipment. The variable temperature test box is filled with liquid oxygen sprayer to complete the actual effect of rapid cooling.

3. Heating system:

The heating system of the high and low temperature box is very simple compared to the refrigeration system. It is composed of high-power resistance wires. Because the temperature-raising speed specified by the test box is relatively large, the output power of the heating system of the test box is very large. , and the bottom plate of the test box is also equipped with an electric heater.