How to read the value of thermometer?

Read the temperature of the thermometer. The temperature of the thermometer increases upward, and each unit increases by 0.5 degrees Celsius. Read the relative humidity from below the dial. The relative humidity decreases from left to right, and each cell is 2%. The hygrometer shows not the degree but the percentage, and the indoor humidity in normal life should be kept at about 45%-70%.

In metrology, humidity is defined as "the amount of image state". Humidity in daily life refers to relative humidity, expressed in RH%. In a word, it is the percentage of saturated water vapor (saturated water vapor pressure) of gas (usually air) under the same conditions as its air.

The relationship between humidity and life has a long history, but it is difficult to express it quantitatively. The expression methods of humidity include absolute humidity, relative humidity, dew point, the ratio of moisture to dry gas (weight or volume) and so on.

Precautions:

In principle, there are twenty or thirty kinds of thermometers to measure humidity. But humidity measurement has always been one of the famous problems in the field of measurement in the world. A seemingly simple numerical value, which is studied deeply, involves quite complicated theoretical analysis and calculation of physical chemistry. Beginners may ignore many factors that must be paid attention to in humidity measurement, thus affecting the rational use of sensors.

Common humidity measurement methods include: dynamic method (double pressure method, double temperature method and shunt method), static method (saturated salt method and sulfuric acid method), dew point method, dry and wet bulb method and electronic sensor method.

1, double pressure method and double temperature method are based on the equilibrium principle of thermodynamics P, V and T, and the equilibrium time is long. The split-flow method is based on the precise mixing of absolute humidity and absolute dry air. Due to the adoption of modern measurement and control means, these devices can be made quite precise, but because of their complexity, high cost and time-consuming operation, they are mainly used for standard measurement, and the measurement accuracy can reach more than 2% RH.

2. Saturated salt method in static method is the most commonly used method in humidity measurement, which is simple and easy to operate. However, the saturated salt method has strict requirements on the balance of liquid and gas phases and the stability of environmental temperature. Balance takes a long time, and the low humidity point is longer. Especially when there is a big difference between the indoor humidity and the humidity in the bottle, it needs to be balanced for 6~8 hours each time.