My experience in repairing a constant temperature and humidity test chamber

The constant temperature and humidity test chamber is the most common environmental testing equipment. Although its popularity is second only to ovens, and with the pursuit of equipment quality by users, the operation of the constant temperature and humidity test chamber is relatively convenient nowadays. However, whether it is cheap or expensive equipment maintenance, it is particularly cumbersome, which leads to users not being able to maintain the equipment in a timely manner and easily accumulating faults and frequent maintenance accidents.

The most common malfunction of the constant temperature and humidity test chamber is humidity malfunction. There are many articles online about repairing the causes of humidity malfunctions, and they are all very general. Below, I will share with you a special humidity fault of the constant temperature and humidity test chamber.

After setting the temperature to 60 degrees and humidity to 85% on the operating instrument of the constant temperature and humidity test chamber, the equipment starts to operate with sufficient water source in the water tank. After a period of time, the equipment can be heated to 60 degrees normally, but the humidity only shows about 3% or 5%, and the boiler is also very hot. The dry and wet bulb sensors are normal, the instrument and solid state can output normally, the corresponding water cup is not short of water and can supply water to the boiler normally. The over temperature protector does not alarm, and the path and thermistor of the humidifier tube are normal when measured by the multimeter. There is AC220V voltage at both ends of the humidifier tube, but there is no steam coming out from the steam outlet of the boiler. This is because under certain purity conditions, water can form a conductor that connects the originally burnt humidification tubes to form a circuit. Therefore, although the humidification tubes are burnt out, they can still generate heat and heat the boiler water, but they cannot boil and produce steam. The simplest way to solve this problem is to use a clamp multimeter to measure the current of the humidifier tube during operation. Given the power and voltage of the humidifier tube, the measured current can be compared with the calculated current. For example, if the humidifier tube is rated at AC220V and 2KW, its current at full power can be calculated to be around 10A. When the measured current is significantly low, it can be determined that the humidifying tube is burnt out, without assuming that the water in the boiler is hot and thinking that the humidifying tube is normal, and finding other fault points.

Although the explanation for this fault is simple, such faults are very rare because when the humidifier or electric heating tube is in a broken state after burning out, it has lost its ability to conduct and will not generate heat. Therefore, by chance, when other substances redo the conductor and connect it, the humidifier tube will restore some of its heating function.