The working principle and work process of the test box system
The principle of the constant temperature constant wet box: Comprehensive The test box consists of refrigeration system, heating system, control system, temperature system air circulation system, and sensor system. The above system is divided into two aspects of electrical and mechanical refrigeration. Here are preliminary description of the working principles and process of several main systems.
Sensor system: The sensor of the test box is mainly temperature and humidity sensor. The temperature sensor is more applied with platinum and thermocouple. There are two ways to measure humidity: dry and wet ball thermometer and solid -state electronic sensor directly measurement method. Due to the low measurement accuracy of the dry and wet ball method, the current test box is gradually measured by the solid -state sensor instead of the dry and wet balls to measure the humidity.
Refrigeration system: The refrigeration system is one of the key parts of the comprehensive test box. Generally speaking, the refrigeration method of the test box is mechanical refrigeration and auxiliary liquid nitrogen refrigeration. Mechanical refrigeration uses steam compressed refrigeration. They are mainly composed of compressors, condenser, throttle, and evaporator. To meet -55 ° C, a single-level refrigeration is difficult to meet the requirements. Therefore, the refrigeration method of a comprehensive test box generally uses folded refrigeration. Heating system: The heating system of the test box is relatively simple. It mainly has a high -power resistance wire composition. Due to the high temperature increase rate required by the test box, the heating system of the test box is relatively large, and the bottom plate of the test box also has a heater.
The moisturizing method of the test box generally uses the steam humidification method, and the low -voltage steam is directly injected into the test space to humidify. This humidification method is moisturizing, fast speed, and sensitive humidification control, especially for compulsory humidification when cooling. There are two types of dehumidification methods of the test box: mechanical refrigeration and dehumidification and dry dehumidification. The principle of mechanical refrigeration and dehumidification is to cool the air below the dew point temperature, so that the water vapor condensation greater than saturated is condensed, which reduces the humidity. The dryer dehumidification uses the air pump to pull out the air in the test box, and injects the dry air. At the same time, the wet air is sent to the circulaable drying to dry it. After drying, send it to the test box. Repeat loop dehumidification. Now most of the comprehensive test box adopts the first method of dehumidification method, and the latter dehumidification method can make the dew point temperature reaches 0 ° C.