Wet and dry thermometer Wet and dry bulb thermometer is an instrument for measuring air temperature and air humidity. 

Structure: It consists of two identical ordinary thermometers, one for measuring air temperature, called dry bulb thermometer; the other is wrapped with gauze soaked in distilled water at the bulb, and the lower end of the gauze is immersed in distilled water, called wet bulb thermometer. 

Because the gauze wrapped around the wet bulb thermometer absorbs water and evaporates and absorbs heat, the reading is smaller than that of the dry bulb thermometer. The gauze of the wet bulb needs to be replaced frequently. When the air is dry, 

the gauze of the wet bulb thermometer evaporates quickly and absorbs more heat, so the reading difference between the two thermometers is relatively large. 

The greater the reading difference between the two thermometers, the drier the air.

When there is a lot of water vapor in the air, the gauze of the wet bulb thermometer evaporates slowly and absorbs less heat, so the reading difference between the two thermometers is small. 

The smaller the reading difference between the two thermometers, the more humid the air. Disadvantages: The test is not accurate, and it can be replaced by a thermometer and hygrometer with electronic display. The psychrometer is an instrument for measuring the humidity in the air. 

The introduction is as follows: When there is a lot of water vapor in the air, we say that the air is humid.