An aneroid barometer is a laboratory instrument used to measure atmospheric pressure. It is a mechanical device that consists of a sealed metal chamber, which is partially evacuated and connected to a needle or pointer that moves in response to changes in atmospheric pressure.

The metal chamber is typically made of a thin, corrugated metal that expands and contracts with changes in pressure. The pointer is attached to the metal chamber and moves in response to the expansion and contraction of the chamber, indicating changes in pressure on a calibrated scale.

Aneroid barometers are smaller and more portable than traditional mercury barometers, making them suitable for use in field applications such as weather forecasting, aviation, and hiking. They are also commonly used in homes and businesses for monitoring changes in atmospheric pressure.