What Is a Humidity Gauge?

Physical property analysis instrument for measuring gas humidity. Humidity indicates the water vapor content in a gas. There are two ways to express absolute humidity and relative humidity. Absolute humidity refers to the absolute content of water vapor in a gas. The most commonly used unit is g / m ^ 3. At a certain temperature and pressure, the water vapor content in a unit volume has a certain limit, which is called the saturated water vapor content. Relative humidity refers to the ratio of the absolute content of water vapor in a gas to the content of saturated water vapor in the same volume of gas at the same temperature and pressure. The commonly used symbol is% RH. Hygrometers have a wide range of applications. For example, in the production processes of ultra-pure metal smelting, textile processing, papermaking and printing and dyeing, as well as food storage and meteorological measurement, hygrometers are often used to measure or control the humidity of air or industrial process gases. ^[1]

Hygrometer consists of two identical

The principle of hygrometer measuring complete relative humidity: The temperature of the wet bubble thermometer is always lower than that of the dry bubble thermometer because the cotton bubble is covered with cotton yarn, and the lower end of the cotton yarn is immersed in water. The temperature difference is related to the speed of water evaporation (that is, the relative humidity at that time). According to the readings of the two thermometers, the relative humidity of the air can be found from the table or the curve.

A hygrometer is an instrument that measures the humidity of the surrounding gas. Humidity is the water vapor content of the gas, divided into

The humidity of the air can be commonly understood as the humidity of the air. It has absolute humidity and relative humidity.

1 . Absolute humidity: The pressure P of water vapor in the air is called the absolute humidity of the air.

Hygrometer

The humidity of air can be expressed by the density of water vapor in air, that is, the mass of water vapor in air per unit volume. Since it is difficult to directly measure the density of water vapor in the air, and the pressure of water vapor increases with the increase of the density of water vapor, the humidity of air is usually expressed by the pressure of water vapor in air, which is the absolute humidity of air.

2 . Relative humidity

(1) Introduction of concept: In order to indicate the distance of water vapor from the saturated state, the concept of relative humidity is introduced.

(2) Relative humidity B: The absolute humidity p of the air at a certain temperature and the percentage of the saturated vapor pressure ps of water at the same temperature are called the relative humidity of the air at this time.

The saturated vapor pressure of water at different temperatures can be found in a table

When the absolute humidity p is constant and the temperature is reduced, the relative humidity of the air is increased because the saturated vapor pressure of water is reduced.

The relative humidity of the room should be 60% 70%. ^[3]