aneroid

An aneroid is an instrument for measuring atmospheric pressure without the use of a liquid. The name refers to devices that rely on the elastic properties of a sealed, evacuated chamber rather than a column of mercury or water. The most common form, the aneroid barometer, uses a thin-walled metal capsule that expands and contracts as external air pressure changes. The capsule is connected to a linkage and gear train that magnifies its motion to drive a pointer on a calibrated dial.

Aneroid mechanisms are also used as altimeters in aircraft. In these instruments, changes in ambient pressure are translated into altitude readings by a calibrated scale. Some compact devices serve as portable barometers or as components inside weather stations. The principle can be implemented with multiple capsules in parallel to improve sensitivity and temperature compensation, and is sometimes integrated into more complex meteorological instrumentation.

Applications and considerations: Aneroids are valued for being rugged, compact, and free of liquid spills, making them widely used in weather instruments, aviation, and consumer barometers. They can be affected by temperature variations, mechanical wear, and vibration, leading to drift over time. Regular calibration or adjustment is often required to maintain accuracy. While not as precise as some liquid-filled instruments, aneroid devices offer practical reliability in a range of environmental conditions.