What instrument is primarily used to measure atmospheric pressure?

The primary instrument used to measure atmospheric pressure is the barometer. A barometer operates based on the principle that changes in atmospheric pressure will affect the height of a column of liquid or the movement of a spring within the device. There are different types of barometers, including mercury and aneroid types, each utilizing different mechanisms to indicate pressure changes.

Understanding atmospheric pressure is crucial in various fields, including meteorology, as it helps predict weather patterns and understand environmental conditions. The barometer's ability to provide real-time pressure readings allows for the monitoring of weather changes, making it an essential tool in both scientific research and everyday weather forecasting.

In contrast, a thermometer measures temperature rather than pressure, an altimeter is primarily used in aviation to determine altitude by measuring air pressure, and a hydrometer measures the specific gravity of liquids, which is unrelated to atmospheric pressure.