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Barometer

The Altimeter

An important application of the aneroid barometer is the altimeter, an instrument used to measure one's distance above sea level. Atmospheric pressure is a function of altitude. The farther one is above sea level, the less the atmospheric pressure, and the closer one is to sea level, the greater the atmospheric pressure. A simple aneroid barometer can be used to confirm these differences. If the barometer is now mounted in an airplane, a balloon, or some other device that travels up and down in the atmosphere, one's height above the ground (or above sea level) can be found by noting changes in atmospheric pressure.


Resources

Books

Banfield, Edwin. Barometers: Aneroid and Barographs. Trowbridge, Wiltshire, England: Baros Books, 1985.

Brombacher, W. G. Mercury Barometers and Manometers. Washington, DC: U.S. Department of Commerce, National Bureau of Standards, 1960.

The Illustrated Science and Invention Encyclopedia. Westport, CT: H. S. Stuttman, 1982, vol. 2: 238-40.

Middleton, W. E. Knowles. The History of the Barometer. Baltimore: Johns Hopkins Press, 1964.


Periodicals

Caristi, Anthony J. "Build a Portable Barometer." Popular Electronics (January 1994):31-6.

Walker, Jearl. "Making a Barometer that Works with Water in Place of Mercury," Scientific American. (April 1987):122-27.


David E. Newton

KEY TERMS

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Altimeter

—An aneroid barometer used to measure altitude.

Barograph

—An aneroid barometer modified to give a continuous reading of atmospheric pressures on graph paper.

English Kew barometer

—A mercury barometer with a contracting measuring scale and a constant reservoir of mercury.

Fortin barometer

—A mercury barometer with a fixed measuring scale and an adjustable reservoir of mercury.

Vapor pressure

—The amount of pressure exerted by liquid molecules in the vapor state.

Vernier scale

—A movable scale for measuring a fractional part of one division on a fixed scale.

Additional topics

Science EncyclopediaScience & Philosophy: Ballistic galvanometer to Big–bang theoryBarometer - Mercury Barometers, Aneroid Barometer, The Altimeter