What instrument is used to measure humidity?

The instrument used to measure humidity is a hygrometer. Hygrometers are specifically designed to measure the amount of water vapor present in the air. There are various types of hygrometers, including mechanical and electronic versions, which utilize different methods to assess humidity levels, such as hair tension or electronic sensors.

Understanding humidity is crucial for meteorology, climatology, and various applications such as weather forecasting and agriculture, as it affects temperature perception, weather patterns, and plant growth. In contrast, other instruments mentioned, like barometers, thermometers, and anemometers, serve different functions; barometers measure atmospheric pressure, thermometers determine temperature, and anemometers gauge wind speed. Therefore, the hygrometer is the only instrument among the options that specifically provides a measurement of humidity.