Editing Barometer (section)

=== Aneroid barometers ===
[[File:Modern Aneroid Barometer.jpg|thumb|Aneroid barometer]]

An aneroid barometer is an [[Measuring instrument|instrument]] used for measuring air pressure via a method that does not involve [[liquid]]. Although Gottfried Wilhelm Leibniz first proposed the concept of an aneroid barometer around 1700, it was not until 1844 that French scientist Lucien Vidi successfully invented it.<ref name="http://www.islandnet.com/~see/weather/history/barometerhistory1.htm" /> The aneroid barometer uses a small, flexible metal box called an aneroid cell (capsule), which is made from an [[alloy]] of [[beryllium]] and [[copper]].<ref name="r1">{{cite book |author1=Figuier, Louis |url=https://archive.org/details/bub_gb_Cus0AAAAMAAJ |title=L'Année scientifique et industrielle |author2=Gautier, Émile |publisher=L. Hachette et cie. |year=1867 |pages=[https://archive.org/details/bub_gb_Cus0AAAAMAAJ/page/n495 485]–486}}</ref> The evacuated capsule (or usually several capsules, stacked to add up their movements) is prevented from collapsing by a strong spring. Small changes in external air pressure cause the cell to expand or contract.  This expansion and contraction drives mechanical levers such that the tiny movements of the capsule are amplified and displayed on the face of the aneroid barometer.  Many models include a manually set needle which is used to mark the current measurement so that a relative change can be seen. This type of barometer is common in homes and in [[recreational boat]]s. It is also used in [[meteorology]], mostly in [[barograph]]s, and as a pressure instrument in [[radiosonde]]s.

==== Barographs ====

{{Main article|Barograph}}

[[File:Barograph 01.jpg|thumb|Analogue recording [[barograph]] using five stacked aneroid barometer cells]]A barograph is a recording aneroid barometer where the changes in atmospheric pressure are recorded on a paper chart.

The principle of the barograph is same as that of the aneroid barometer. Whereas the barometer displays the pressure on a dial, the barograph uses the small movements of the box to transmit by a system of levers to a recording arm that has at its extreme end either a scribe or a pen. A scribe records on smoked foil while a pen records on paper using ink, held in a nib. The recording material is mounted on a cylindrical drum which is rotated slowly by a clock. Commonly, the drum makes one revolution per day, per week, or per month, and the rotation rate can often be selected by the user.