Which instrument is used to measure atmospheric pressure?

A barometer is specifically designed to measure atmospheric pressure, which is a crucial aspect of meteorology and weather forecasting. Atmospheric pressure is the force exerted by the weight of air above a given point, and it plays a significant role in determining weather patterns. The barometer works by either using mercury in a column or an aneroid capsule that expands or contracts with changes in air pressure, enabling precise measurement.

Understanding atmospheric pressure is vital for pilots and meteorologists because it affects flight performance, weather predictions, and the exploration of phenomena such as storms and front systems. When atmospheric pressure changes, it can indicate shifts in weather conditions, such as the approach of a high or low-pressure area, which are key to forecasting.

The other instruments have distinct purposes: a psychrometer measures humidity, an anemometer is used to measure wind speed, and a hydrometer is designed to measure the density or specific gravity of liquids. Therefore, the barometer is correctly identified as the tool that specifically and directly measures atmospheric pressure.