aneroidbaromeeter

An aneroid barometer is a pressure-measuring instrument that determines atmospheric pressure without using liquid. It operates with a sealed, flexible metal chamber, known as an aneroid cell or capsule, which is evacuated so it can expand or contract as external air pressure changes. The capsule’s deflection is transmitted through a system of levers and springs to a pointer on a dial, which is calibrated in units such as hectopascals (hPa) or inches of mercury (inHg). Temperature effects are often compensated in more refined designs to improve accuracy.

History and name

The device was popularized in the 19th century by French instrument maker Lucien Vidie, who developed the first practical aneroid barometer around 1843. The term aneroid comes from Greek roots meaning “without liquid,” distinguishing it from liquid-filled barometers.

Construction and variants

An aneroid barometer consists of a sealed capsule, a linkage mechanism to amplify its small motions, a case, and a dial with a scale. Some variants integrate a microaneroid system for higher sensitivity or use multiple capsules in parallel to increase stability. In aviation, the same principle underpins the altimeter, which translates ambient pressure into altitude, with corrections for temperature and local pressure settings.

Operation and applications

In meteorology, aneroid barometers monitor pressure changes and trends for weather forecasting. Portable models serve in fieldwork and educational settings. In aviation and mountaineering, compact aneroid barometers and altimeters provide essential altitude or pressure information. They are often paired with barographs or continued to be used in weather stations as a robust, liquid-free alternative to mercury-based instruments.

Advantages and limitations

Aneroid barometers are rugged, compact, and free of mercury spill risk. They are sensitive and require careful calibration, temperature compensation, and periodic maintenance; their absolute accuracy is generally lower and more susceptible to drift than high-quality liquid barometers.