A psychrometer is an instrument used to measure the moisture content or humidity of the air. It typically consists of two thermometers: a dry-bulb thermometer that measures the ambient air temperature and a wet-bulb thermometer, which is moistened and provides a reading that reflects the cooling effect of evaporation. The difference in readings between the two thermometers allows for the calculation of relative humidity. Psychrometers are commonly used in meteorology, HVAC systems, and various industrial applications.