Aneroid barometers work on the principle of the expansion and contraction of a metal chamber, known as the aneroid capsule. This capsule is made up of a thin, corrugated metal, usually beryllium copper. The capsule is sealed and partially evacuated of air, so it is very sensitive to changes in atmospheric pressure.
When atmospheric pressure increases, the pressure inside the capsule decreases, and the capsule contracts. This contraction is transmitted to a mechanical linkage that moves the pointer of the barometer. When atmospheric pressure decreases, the capsule expands and the pointer moves in the opposite direction.
Aneroid barometers are widely used because they are portable, compact, and easy to read. They are often used in weather stations, homes, and airplanes.
