Working principle of hygrometer
A, the common form of humidity controller
Hair hygrometers, wet and dry bulb hygrometers, and resistive and capacitive humidity sensors and transmitters. Here are some commonly used hygrometers.
(1) Working principle of hair humidity controller: When the relative humidity of air changes, human hair and nylon filament (or film) will expand and contract. For example, when the humidity changes 10%, the length of the selected degreasing wool changes? 2%。 Using this principle, one end of a bundle of defatted hair is fixed, and when it senses the change of humidity, the other end transmits a displacement signal to drive the pointer, which can display the humidity; The displacement of that humidity control is converted into an electric switch action, and the humidity control can be used as a humidity controller to adjust the humidity of air by cooperating with a humidify solenoid valve or a dehumidifying cooling coils solenoid valve.
(2) Working principle of hair hygrometer: Based on the principle that water evaporates to absorb heat and cool down, the evaporation speed (that is, the amount of cooling down) is related to the relative humidity of the air at that time. According to the difference between the dry bulb temperature and the wet bulb temperature, the electrical switch is started. Two resistive temperature sensors are used, one to measure the temperature of dry bulb and the other to measure the temperature of wet bulb wrapped with wet gauze.
The signal is amplified by electronic circuit to control the action of electric contact. At this time, there is a corresponding relationship between the temperature difference between wet bulb and dry bulb and the relative humidity of the environment, but this relationship is nonlinear. When measuring the temperature of dry and wet bulb, a small fan should be used for forced air blowing, and the wind speed at the measuring point of wet bag should be kept at 3 ~ 4 m/s. Because water is used for measuring the temperature of wet bulb, this hygrometer can only measure humidity in an environment above 0℃.
? Measurement method:
First of all, you need to fill the sink with water and let the gauze wrap the thermometer, which means that the gauze of the wet ball can be in a wet state, then observe the values of the two thermometers and read them out with a dial!
Insert the dry bulb and wet bulb colleagues into the water to see if the readings of the two thermometers are the same. A difference of 2 degrees is considered unqualified!
The above is the introduction of the working principle of the temperature and humidity instrument. I believe many friends have understood the working principle of the temperature and humidity meter. The working principle of the temperature and humidity instrument is very simple, and the sensor design is adopted. The sensor can sense humidity and temperature and realize the function of electronic measurement. When we use the temperature and humidity instrument, we should remember to fix it, because this kind of equipment needs to be in a stable environment to measure accurately, and we can't keep walking and shaking.