An instrument for measuring atmospheric pressure. It is constructed on the following principles: An aneroid capsule (a thin corrugated hollow disk) is partially evacuated of gas and is restrained from collapsing by an external or internal spring; the deflection of the spring will be nearly proportional to the difference between the internal and external pressures; magnification of the spring deflection is obtained both by connecting capsules in series and by mechanical linkages. The aneroid barometer is temperature compensated at a given pressure level by adjustment of the residual gas in the aneroid or by a bimetallic link arrangement. The instrument is subject to uncertainties due to variations in the elastic properties of the spring and capsules, and due to wear in the mechanical linkages. See barometer, aneroid barograph, pressure altimeter, altimeter-setting indicator.