A barometer is a scientific instrument that can measure air pressure. With the aid of this information, weather changes can be predicted, altitude can be determined, and scuba divers' air tanks can be monitored, among other uses.
Although Galileo Galilei's student Evangelista Torricelli is credited as the barometer's inventor, many other 17th-century scientists developed studies and techniques that were either headed in the same direction or made this invention possible. Among them are Galileo himself, Gasparo Berti, René Descartes, Giovanni Battista Baliani, Blaise Pascal, and Marin Mersenne.
There are different types of barometric systems. The most common are water-based, mercury, aneroid, and MEMS barometers. The first consists of a sealed container that is half-filled with water; the water level varies according to air pressure oscillations. Mercury barometers operate on the same principle, but international mercury bans have halted their production. French scientist Lucien Vidie invented aneroid barometers in 1844; their main element is a flexible capsule (aneroid cell) that expands and contracts as external pressure changes.
Finally, MEMS barometers (an acronym for microelectromechanical systems) also detect atmospheric pressure variations due to their effect on a flexible structure. The degree of expansion or contraction is translated into an electrical signal – differently from aneroid barometers, which rely on mechanical components. Current MEMS technology allows for these sensors to be minuscule enough to be integrated into virtually any product. This is the digital barometric technology built into mobile devices and wearables, improving GPS precision and, in some cases, providing altitude readings. Readings are based upon standard sea-level air pressure and rely on optimal calibration for accuracy.