The instrument used for measuring atmospheric pressure is

The instrument used for measuring atmospheric pressure is a barometer. A barometer is an instrument that measures atmospheric pressure and is commonly used in weather forecasting. It works by balancing the weight of mercury or aneroid capsules with the weight of the atmosphere. As air pressure changes with the weather, the mercury or capsule moves up or down, indicating changes in pressure. The unit of measurement for atmospheric pressure is usually in millibars or inches of mercury (inHg).