A psychrometer is a device used to measure the humidity in the air. It consists of two thermometers: a dry bulb thermometer that measures the air temperature and a wet bulb thermometer that has a moistened wick. The difference in temperature readings between the two thermometers helps determine the relative humidity. Psychrometers are commonly used in meteorology, HVAC systems, and various industrial applications. By calculating the evaporation rate from the wet bulb, users can assess how much moisture is in the air, which is essential for weather forecasting and maintaining comfortable indoor environments.