In the process of using the constant temperature and humidity test box, many laboratories will find that the temperature and humidity of the test box cannot go up or down. Why is this? Summarize the following four points:

1. The high temperature of the thermostatic bath cannot go up

In the high temperature test, if the temperature change does not reach the required test temperature value, you can check the electrical system of the constant temperature equipment and troubleshoot one by one. If the temperature rises very slowly, it is necessary to check the air circulation system of the constant temperature equipment to see if the regulating baffle of the air circulation of the constant temperature equipment is open normally; otherwise, check whether the motor of the air circulation of the constant temperature tank is running normally. If the temperature overshoot is severe, it is necessary to adjust the setting parameters of the PID of the constant temperature bath. If the temperature will rise directly, over-temperature protection, then the controller is faulty, and the control instrument must be replaced.

2. The thermostatic bath will not go under low temperature

If the low temperature does not reach the test index, then you must observe the temperature change of the constant temperature bath. Whether the temperature drops very slowly, or the temperature tends to rise after the temperature reaches a certain value. Dry the working room, keep the working room dry, and then put the test sample into the working room and do the test again. Whether the test sample in the working room is placed too much, so that the wind in the working room cannot be fully circulated. After eliminating the above reasons, It is necessary to consider whether it is a fault in the refrigeration system, so it is necessary to ask the professional personnel of the manufacturer for maintenance. The latter phenomenon is caused by the poor use environment of the equipment. The ambient temperature and placement position of the equipment (the distance between the back of the box and the wall) must meet the requirements (specified in the equipment operation and use instructions).

3. The humidity of the constant temperature tank cannot rise

If the humidity does not rise, it should be that the humidification heating tube is not working. Check whether the heating tube is open, whether the heating circuit is broken or the fuse is burned out due to short circuit; if the fuse is burned out, check whether the solid state relay is broken down during maintenance; if there is no problem with the main circuit, check whether the output end of the controller is damaged.

4. The humidity of the constant temperature tank cannot go down

In the damp heat test, the actual humidity will reach 100% or the actual humidity will be very different from the target humidity, and the value will be much lower. The former phenomenon: it may be caused by the drying of the gauze on the wet bulb sensor, then check the wet bulb sensor. Check whether the water tank is short of water, the water level in the water tank is automatically controlled by a water level controller, check whether the water supply system of the water level controller is normal for water supply, and whether the water level controller works normally. Another possibility is that the wet ball gauze will become hard due to the long use time or the purity of the water supply water, so that the gauze cannot absorb water and dry, and the above phenomenon can be eliminated as long as the gauze is replaced or cleaned. The latter phenomenon is mainly that the humidification system does not work, check the water supply system of the humidification system, whether there is a certain amount of water in the water supply system, whether the water level control of the humidification boiler water level is normal, and whether the water level in the humidification boiler is normal. If all the above are normal, it is necessary to check the electrical control system, which should be repaired by professional maintenance personnel.