As the core equipment for environmental simulation, the humidity control accuracy of the constant temperature and humidity test chamber directly affects the reliability of material testing, product development, and other processes.When the humidity in the test chamber cannot be reduced, a systematic investigation should be carried out from four dimensions: equipment hardware, control system, environmental factors, and operating standards.

　　1、 Deep diagnosis of hardware system failures

The refrigeration system is the foundation of humidity control. Compressor failure, refrigerant leakage, or poor heat dissipation of the condenser can all cause the surface temperature of the evaporator to fail to drop below the dew point, thereby weakening the dehumidification ability. It is necessary to detect the refrigerant pressure through a pressure gauge and determine the heat dissipation efficiency based on the surface temperature of the condenser. Meanwhile, if the desiccant (such as molecular sieve) in the dehumidification device is not replaced for a long time, it will become ineffective due to adsorption saturation and needs to be regularly regenerated or replaced.

Another common reason is the imbalance between humidification and dehumidification systems. The humidifier solenoid valve is stuck, the water pipe is blocked, or the position of the humidification cloth is offset, which may cause continuous moisture input and counteract the dehumidification effect. It is necessary to check the smoothness of the humidification water circuit, confirm that the wet cloth is in close contact with the sensor, and avoid false humidity signals.

　　2、 Accurate calibration of control systems and sensors

As the control core, the position deviation or performance degradation of humidity sensors can directly lead to control failure. Sensors should be kept away from heat sources, humidity sources, and ventilation openings, and should be calibrated regularly with a standard humidity source. If the sensor signal transmission line is affected by electromagnetic interference, it may cause misjudgment in the control program, and the integrity of the shielding layer and grounding reliability need to be checked.

Control system program errors or improper parameter settings are equally critical. For example, PID control parameters not optimized according to device characteristics may result in delayed or excessive dehumidification actions. It is necessary to analyze the execution status of control instructions through device logs and contact the manufacturer to update the firmware if necessary.

　　3、 Collaborative optimization of environmental factors and operational standards

The constant temperature and humidity test chamber is located in an environment with high humidity (if not equipped with independent air conditioning) or poor ventilation, which can result in external moisture backflow. It is recommended to place the device in a stable temperature and humidity environment, and ensure that the sealing strip of the box is not aging or cracking. Frequent opening and closing of the box door or placing high humidity samples during the operation process will significantly increase the humidity load. It is necessary to standardize the operation process and control the amount of samples for a single test.

　　4、 Preventive maintenance and emergency response mechanism

Establish a hierarchical maintenance system: daily inspection of waterway and circuit connections; Clean the filter screen and evaporator weekly; Calibrate sensors and test refrigerant pressure every month; Replace desiccants and check the operation status of compressors every quarter. At the same time, emergency plans should be developed to automatically trigger alarms and suspend testing when humidity exceeds the limit, in order to avoid the generation of invalid data.