How Does the Temperature Humidity Test Chamber Work?

Temperature humidity testing chamber is also known as temperature humidity testing machine, constant temperature machine or constant temperature and humidity chamber. It is mainly used to test the properties of materials in various environments, such as cold resistance, heat resistance, moisture resistance, dry resistance and so on. So what is the working principle of the temperature humidity testing chamber?

The temperature humidity testing chamber is composed of refrigerating system, heating system, control system, humidity system, air supply circulating system, sensor system. It works mainly by these systems.

Refrigeration System 

The refrigeration system is one of the key parts of the temperature humidity testing chamber. The refrigeration system of the temperature humidity testing chamber is composed of two parts, which are high temperature part and low temperature part. Each part is a relatively independent refrigeration system. In the high temperature part, the refrigerants vaporize by absorbing the heat of the refrigerants in the low temperature part. In the low temperature part, the evaporation of refrigerants absorbs heat from the cooled object (air in the testing chamber) .

Heating System 

The heating system of the humidity and temperature controlled chamber is relatively simple compared with the refrigeration system. It is mainly composed of high power resistance wire. Because of the high heating rate required by the benchtop humidity chamber, the heating system power of the testing chamber is relatively large, and there is also a heater on the bottom plate of the temperature humidity testing chamber. 

Control System

The control system is the core of the temperature humidity testing chamber, which determines the heating rate, precision and other important indexes of the testing chamber. 

Humidity System

The humidity system is divided into two subsystems: humidification system and dehumidification system. The humidification method is generally steam humidification. The low-pressure steam is directly injected into the testing chamber to humidify. This humidification method has strong humidification ability, fast speed and sensitive humidification control. 

There are two ways of dehumidification: mechanical refrigeration dehumidification and dryer dehumidification. The principle of mechanical refrigeration dehumidification is to cool the air below the dew point temperature. Then the water vapor which is larger than the saturation humidity ratio content condenses and separates out , thus reducing the humidity. The air pump is used for drawing the air in the tenvironmental chamber manufacturers, and the dry air is injected. Then the humid air is sent to a dryer which can be recycled for drying, after the drying is finished, the air is sent to the testing chamber, so that the dehumidification is carried out repeatedly. 

Air Supply Circulating System

The air supply circulation system is generally composed of a centrifugal fan and a motor for driving it. It provides a cycle of air in the testing chamber. 

Sensor System

The sensor is mainly divided into temperature and humidity sensors. Platinum resistance and thermocouple are widely used in temperature sensors. There are two methods for measuring the humidity:  psychrometer measurement method and electronic sensor measurement method. Due to the low measurement precision of the former, the present temperature humidity testing chamber is gradually taking the electronic sensor instead of the psychrometer to measure the humidity.