|aneroid barometer (ān'ə-roid') Pronunciation Key
(click for larger image in new window)
A barometer consisting of a thin elastic disk covering a chamber that contains a partial vacuum. High atmospheric pressure pushes against the disk and causes it to bulge inward, while low pressure does not push as hard, allowing the disk to bulge outward. An aneroid barometer is smaller and more portable than a mercury barometer and, when used with a barograph, can record up to a week's worth of data. Aneroid barometers are used extensively in aviation as part of altimeters.