Which instrument is primarily used to measure atmospheric pressure?

The instrument primarily used to measure atmospheric pressure is the barometer. Barometers function by balancing the weight of the atmosphere against a column of liquid, typically mercury in traditional barometers, or utilizing an aneroid capsule in more modern designs. Changes in atmospheric pressure can significantly affect weather patterns and conditions, making accurate measurements crucial for meteorological observations.

In contrast, a hygrometer measures humidity, indicating the amount of moisture in the air. An anemometer is designed to measure wind speed and direction, while a thermometer measures temperature. Each of these instruments serves a specific purpose in weather observation, but for measuring atmospheric pressure, the barometer remains the standard and most effective choice.