Why should the humidity probe of the constant temperature and humidity test chamber be wrapped with a wet cloth?

At present, the standard constant temperature and humidity test chamber in the industry mostly uses the dry-bulb temperature comparison output to test humidity. The difference between the dry-bulb temperature and the humidity value at a fixed wind speed is certain, and this difference is obtained by wrapping a wet cloth on the wet bulb. Because the principle of evaporation and heat absorption causes the wet bulb temperature to drop, the wet bulb must be wrapped with a wet cloth.

Humidity is a physical quantity that indicates the dryness of the atmosphere. The less water vapor contained in a certain volume of air at a certain temperature, the drier the air; the more water vapor, the more humid the air. The dryness and wetness of the air is called "humidity". We know that the standard humidity scale of the constant temperature and humidity test chamber is usually: 20%~98%. If there is no humidity cloth, the humidity in the constant temperature and humidity test chamber will display 100%. Simply reflected in the constant temperature and humidity test chamber is that the comparison value of the dry bulb and the wet bulb is directly displayed through the automatic calculation of the PLC.

The hygrometer is composed of two thermometers of the same specifications placed side by side. One of the thermometers is wrapped with a damp piece of cloth. If the atmosphere is dry, the moisture on the wet gauze will evaporate and take away some heat, so the two thermometers will have different readings. Their ratio is the so-called "humidity". The wet cloth in the constant temperature and humidity test chamber is used on the "hygrometer", a small accessory for measuring air humidity. After the moisture in the gauze evaporates, the thermometer must be replenished with water so that it can continue to work reliably. Therefore, the humidity probe in the constant temperature and humidity test chamber must be wrapped with a wet cloth to work.