Common types of humidity controllers include hair hygrometers, dry and wet bulb hygrometers, and resistance and capacitance humidity sensors and transmitters. Sewing Supplies,Sewing Product,House Hold Sewing,Sewing Thread Collection,Sewing Items OYEAL Global , https://www.oyealhome.com
(1) Working principle of hair type hygrometer: Human hair, nylon filament (or film) will expand and contract when the relative humidity of the air changes. For example, when the humidity of the selected degreased hair changes by 10%, the length changes by 2%. Using this principle, one end of a bundle of degreased hair is fixed. When it senses the change in humidity, the other end is transmitted with a displacement signal, which drives the pointer to display the humidity; the displacement is converted into an electric switch action: The dehumidification cooling coil solenoid valve can be used as a humidity controller to adjust the humidity of the air.
(2) Working principle of wet and dry bulb hygrometer: It uses the principle of humidity measurement of air wet and dry bulb thermometer, according to the difference between dry bulb temperature and wet bulb temperature, to make the electric switch act. Two resistance temperature sensors are used, one to measure the temperature of the dry bulb and one to measure the temperature of the wet bulb with a wet gauze. Amplify the signal with an electronic circuit to control the action of electrical contacts. In the wet and dry bulb temperature measurement, a small fan is used to force the blowing, and the wind speed at the measurement point of the wet pack is maintained at 3 to 4 m / s. Because water is used in the measurement of wet bulb temperature, this hygrometer can only measure humidity in an environment above 0 ° C.
(3) Working principle of electronic hygrometer: There are many kinds of metal salts (for example, lithium chloride, calcium chloride) which have strong hygroscopicity in the air. Moisture absorption increases the moisture in the salt; until the moisture in the salt and the moisture in the air reach equilibrium. The equilibrium water content of the salt corresponds to the relative humidity of the air. The greater the relative humidity, the greater the equilibrium water content in the salt and the lower the resistance of the salt; conversely, the lower the relative humidity of the air, the greater the resistance of the salt. Use this principle to use lithium chloride as a resistance humidity transmitter for humidity measurement and control.