Which instrument is used to measure humidity in the environment?

• A. Barometer
• B. Thermometer
• C. Hygrometer
• D. Anemometer

Answer: (C)

Humidity is the amount of water vapor in the air, and to measure it you use a hygrometer. This instrument directly senses the moisture content of the air and usually provides a reading as relative humidity, often shown as a percentage. There are different kinds of hygrometers, such as mechanical ones that respond to humidity through material expansion or contraction, and electronic ones that use capacitive or resistive sensors to detect changes in moisture. Some hygrometers are paired with a thermometer to relate humidity to temperature and sometimes to calculate dew point.

The other instruments measure different environmental properties: a barometer gauges atmospheric pressure, a thermometer measures temperature, and an anemometer measures wind speed. Since they do not quantify water vapor in the air, they’re not used to measure humidity.