What instrument is used to measure air pressure?

The instrument used to measure air pressure is the barometer. Barometers function by utilizing the principle that air pressure changes with altitude and atmospheric conditions. They typically contain a column of mercury or a flexible membrane that reacts to changes in atmospheric pressure. As air pressure rises, it pushes down on the mercury or the membrane, causing a change in the measurement that can be read on a scale.

In meteorology, barometers are crucial for weather prediction, as they help determine high and low-pressure systems, which are influential in forecasting weather patterns. An altimeter, on the other hand, measures altitude based on atmospheric pressure but is not directly used for measuring air pressure itself. A thermometer measures temperature, while a seismograph detects and records the motion of the ground, particularly during earthquakes. Thus, the barometer stands out as the specific tool designed for measuring air pressure.