Psychrometer consists of two thermometers. One thermometer measures the temperature of the air, and the second bulb is moistened with water. Because water evaporates from the fabric, then the second thermometer is cooled. The intensity of evaporation, and hence the temperature of the second thermometer, depends on the humidity in the room. The action of the hair hygrometer is based on the property of defatted hair to change its length when the air humidity changes. The condensation hygrometer determines the absolute humidity by measuring the dew point.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.