Share the system composition and working principle of the constant temperature and humidity test chamber

What is a constant temperature and humidity test box: Constant temperature and humidity test chamber is also known as constant temperature and humidity test machine, constant temperature and humidity test box, programmable humidity and heat alternating test box, constant temperature machine or constant temperature and humidity box, which is used to test the performance of materials in various environments and test the heat, cold, dry and moisture resistance of
various materials.

Suitable for electronics, electrical appliances, mobile phones, communications, instruments, vehicles, plastic products, metals, food, chemical, building materials, medical, aerospace and other products to test the quality of use
.

As a member of the environmental testing industry, the constant climate chamber is a popular product
.

The equipment is composed of six parts of the heating system, refrigeration system, control system, humidity system, sensor system and air circulation system (1) heating system: The heating system of the constant temperature and humidity chamber is mainly composed of high-power resistance wires, so the heating system power of the test chamber is relatively large, and the heater
is provided on the bottom plate of the test chamber.

(2) refrigeration system: refrigeration system refrigeration methods include mechanical refrigeration and auxiliary liquid nitrogen refrigeration, mechanical refrigeration using steam compression mode, because single-stage refrigeration is difficult to meet the requirements (-55 °C), so the refrigeration mode of the test chamber generally adopts cascade refrigeration, the high temperature part of the refrigerant evaporation absorbs the heat of the refrigerant from the low temperature part and vaporizes; The evaporation of the refrigerant in the cryogenic part is carried out from the cooled object (the air inside the test chamber) to obtain the cooling capacity
.

(3) Control system: it is the core control part of the constant temperature and humidity test box, which determines the heating rate and accuracy of the test chamber; Now most of the controllers of the test chamber use PID control, and a small number of them use the control mode
of combining PID and fuzzy control.

(4) Humidity system: The humidity system of the constant temperature humidity box is divided into two subsystems: humidification and dehumidification; Its humidification method generally adopts steam humidification method (direct injection of low-pressure steam into the test space for humidification), which is fast, humidification control is sensitive, especially in the cooling can easily achieve forced humidification; Its dehumidification methods have two types: mechanical refrigeration dehumidification and drying dehumidification, and now most of the test chambers use mechanical refrigeration dehumidification
.

(5) Sensor system: the sensor of the constant temperature and humidity box is mainly the temperature and humidity sensor, the humidity sensor application is more platinum resistance and thermocouple, humidity measurement methods have two kinds: dry and wet bulb thermometer method and solid-state electronic sensor direct measurement method air circulation system: the air circulation system of the test chamber generally has a centrifugal fan and a motor driving its operation, which provides the circulation
of air in the constant temperature and humidity test chamber.