Which instrument is specifically used to measure air pressure?

The instrument specifically used to measure air pressure is the barometer. Barometers are designed to detect changes in atmospheric pressure, which can indicate weather changes. They operate based on the principle that changes in air pressure are related to weather patterns; for instance, a drop in pressure often signals bad weather, while rising pressure suggests fair weather conditions.

While a thermometer measures temperature, an altimeter is used to determine altitude by measuring the atmospheric pressure and is commonly found in aircraft instruments. An anemometer is used to measure wind speed, not air pressure. Each of these tools has its unique function within meteorology, but the barometer is the dedicated instrument for measuring air pressure specifically.