Basic control of walk-in constant temperature and humidity test room

The walk-in constant temperature and humidity test room is suitable for the low temperature, high temperature, high and low temperature changes, constant heat, high and low temperature alternating damp heat test of the complete machine or large parts. Can change the size and function of the studio according to the user's requirements; block-type box, elegant appearance; scientific design of the air channel, to meet the needs of different customers; using touch screen, PLC program controller.

The walk-in constant temperature and humidity test room consists of a control system, a sensor system, a heating system, a refrigeration system, a temperature system, and an air circulation system. The following Kunshan Haida instrument engineers describe the working principles and working processes of several major systems .

1. Control system: The control system is the core of the comprehensive test box, which determines the temperature rise rate, accuracy, and other important indicators of the test box. Most of the controllers in the test chamber use PID control, and a small number of controllers use a combination of PID and fuzzy control. Since the control system basically belongs to the scope of software, and this part is in use, generally there will be no problem.

2. Sensor system: The sensors of the test chamber are mainly temperature and humidity sensors. Temperature sensors are more commonly used platinum resistance and thermocouples. There are two methods for measuring the humidity: the wet and dry bulb thermometer method and the solid-state electronic sensor direct measurement method. Due to the low accuracy of the wet and dry ball method, the current test box is gradually replacing the wet and dry ball with a solid state sensor for humidity measurement.

3, the heating system: It mainly consists of high-power resistance wire, because the test chamber requires a larger heating rate, so the heating power of the test chamber is relatively large, and the bottom of the test box is also equipped with a heater.

4. Refrigeration system: It is one of the key parts of a walk-in constant temperature and humidity laboratory. In general, the refrigeration method of the test chamber is mechanical refrigeration and auxiliary liquid nitrogen refrigeration. Mechanical refrigeration adopts vapor compression refrigeration. They are mainly composed of a compressor, a condenser, a throttling mechanism and an evaporator, due to the low temperature of our experiment. To reach 55 degrees below zero, single-stage cooling is difficult to meet the requirements, so the refrigeration method generally uses cascade refrigeration.

5, temperature system: walk-in constant temperature and humidity laboratory temperature system is divided into two subsystems humidification and dehumidification. Humidification is generally steam humidification. Dehumidification has two kinds of mechanical refrigeration dehumidification and drying dehumidification.

6. Air circulation system: The air circulation system generally consists of a centrifugal fan and a motor that drives its operation. It provides the circulation of air in the test chamber.