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The Bourdon pressure gauge, patented by the French engineer Eugene Bourdon in 1849, remains one of the most widely used gauges for measuring pressure in liquids and gases of many different types. This is because such gauges are simple to use, safe, and inexpensive, as well as highly accurate. Bourdon tubes are usable when measuring both high pressure and vacuum, and they are important components of devices used to measure various types of pressure, including gauge, absolute, and differential pressure.
Basically, a Bourdon pressure gauge consists of a tube coiled into a spiral shape or helix, or formed into a C shape, so that when the pressure increases, the tube will straighten out. The tube will have an oval cross-section and, usually, one end will be connected to the pressure source. The tube pressure gauge is usually attached to a pointing device or dial so that the slight movements of the tube as it straightens out under pressure can be easily seen and accurately measured in pounds per square inch (psi) or another measurement system. Bourdon tube pressure gauges are available for the many different situations in which someone would need to measure pressure, but they all follow this same basic model.
Such a gauge can be made to be as accurate as 0.1% for precision measurement. For situations in which such a degree of accuracy is unnecessary, cheaper but less precise devices are also available. Bourdon gauges are used to measure pressure in simple devices, such as household barometers, as well as in specialized devices used in industrial, mechanical, and medical settings. The wide range of uses for them and the way in which they can be incorporated into a wide variety of devices greatly contributes to both their usefulness and popularity.
While generally robust in construction, a Bourdon pressure gauge can be damaged by physical force or by exposing the device to conditions for which the particular gauge is not rated, such as extreme temperatures or corrosive liquids. The pressure indicator should return to zero when pressure is removed; if it does not, the gauge is likely damaged and will need to be replaced. Accessories are available that can be used to cushion or protect a gauge from a variety of conditions that may damage it. Blowout protection, safety casing, and weatherproof and corrosion-proof casings should always be used so that, if the device does fail, no material will escape from the casing.