What is a psychrometer used for?

A psychrometer is an instrument specifically designed to measure relative humidity in the atmosphere. It operates based on the principle of evaporation and uses two thermometers: one with a dry bulb that measures the air temperature, and one with a wet bulb that has a moistened wick. The difference in readings between the two thermometers is influenced by the moisture content in the air. As the water from the wet bulb evaporates, it cools down, and the amount of cooling indicates how humid the air is. This allows for the calculation of relative humidity, which is the amount of water vapor present in the air compared to the maximum amount that the air can hold at that temperature.

In contrast, instruments meant for measuring temperature, rainfall, or air pressure do not provide the specific function of assessing humidity levels in the atmosphere as accurately as a psychrometer does.