The principle of the programmable high and low temperature box:
A programmable high and low temperature chamber is a test chamber that can simultaneously apply temperature and humidity stress. With the development of industrial products in China, in recent years, low-temperature water baths have introduced a large number of test systems from abroad, which have played an important role in the development and stereotypes of industrial products in China, but due to their complexity, the test chambers are running. There have been many problems in the process, and problems have not been solved in time, which greatly extended the test cycle and affected the development of the product. To this end, we have made some brief explanations on the basic working principle of the test box, and how to analyze and judge the failure of the test equipment of the comprehensive test chamber. The programmable high and low temperature box is composed of a refrigeration system, a heating system, a control system, a temperature system air circulation system, and a sensor system. The above system belongs to two major aspects of electrical and mechanical refrigeration. The following describes the working principle of several main systems and work process.
Generally speaking, the cooling mode of the test chamber is mechanical refrigeration and auxiliary liquid nitrogen refrigeration. The mechanical refrigeration uses vapor compression refrigeration. They are mainly composed of a compressor, a condenser, a throttle mechanism and an evaporator. The low temperature water tank is tested by us. The temperature is low at -55 °C, and single-stage refrigeration is difficult to meet the requirements. Therefore, the cooling method of the test box generally uses cascade refrigeration. The refrigeration system of the programmable high and low temperature box produced by our company (Yuelian Instrument) consists of two parts. They are called the high temperature part and the low temperature part, respectively, and each part is a relatively independent refrigeration system.
The evaporation of the refrigerant in the high temperature portion absorbs the heat of the refrigerant from the low temperature portion and vaporizes; the evaporation of the low temperature portion of the refrigerant in the high temperature chamber absorbs heat from the object to be cooled (air in the test chamber) to obtain the cold amount. The high temperature portion and the low temperature portion are connected by an evaporating condenser which is both a condenser at a high temperature portion and a condenser at a low temperature portion. The high temperature part of the STH series test chamber uses medium temperature refrigerant, and the low temperature part of the refrigerant uses low temperature refrigerant. The temperature inside the box can reach -70-150 ° C. The heat system power is relatively large, and the bottom plate of the test box is also set. There is a heater.
The control system is the core of the comprehensive test chamber. It determines the important parameters such as the heating rate and accuracy of the test box. Most of the controllers in the test box now use PID control, and a small number of control modes using PID and fuzzy control are combined. Since the control system is basically in the category of software, and this part is in use, there is generally no problem.
Heating system: The heating system of the programmable high and low temperature chamber test chamber is relatively simple compared to the refrigeration system. It mainly consists of high-power resistance wire. Because the temperature rise rate required by the test box is large, the temperature system of the test box is divided into two subsystems: humidification and dehumidification. The humidification method of the test box generally adopts the steam humidification method, that is, the low pressure steam is directly injected into the test space to humidify. This humidification method has the ability to humidify, has a high speed, and is sensitive to humidification, and is particularly easy to achieve forced humidification when cooling. There are two ways to dehumidify the test chamber: mechanical refrigeration dehumidification and dry dehumidification. The dehumidification principle of mechanical refrigeration dehumidification is to cool the air below the dew point temperature, so that the water vapor larger than the saturated moisture content is condensed and precipitated, thus reducing the humidity.
Dehumidification of the dryer uses the air pump to pump out the air in the test chamber, and injects the dry air. At the same time, the humid air is sent to the recyclable dry and dried. After drying, it is sent to the test chamber, and the cycle is dehumidified repeatedly. . Most of the comprehensive test chambers now use the former dehumidification method, and the latter dehumidification method can make the dew point temperature reach 0 °C. Programmable high and low temperature chambers are suitable for occasions with special requirements, but they are more expensive. The sensors in the test chamber are mainly temperature and humidity sensors. The most suitable temperature sensors are platinum batteries and thermocouples. There are two methods for measuring humidity: dry-wet bulb thermometer method and solid-state electronic sensor direct measurement method. Due to the low measurement accuracy of the dry and wet ball method, the current test chamber is gradually replacing the wet and dry balls with solid-state sensors for humidity measurement.
Dongguan Qingsheng Testing Equipment Co., Ltd. adheres to the service tenet of "customer first, quality first", making full use of the technology of environmental testing engineering and reliability engineering for many years, providing customers with high quality, accurate, durable and beautiful testing equipment to ensure Product performance is stable and the life of the equipment exceeds customer expectations. To help customers improve quality, reduce costs and increase market competitiveness.
Votive Glass,Pentagrams Votive Glass,Clear Pentagrams Votive Glass,Votive Glass With Pentagrams
Xi`an ATO International Co., Ltd , https://www.ato-group.com