The closed end of the bourdon tube is attached to a mechanical linkage | Absolute pressure ranges as low as 0 -100 mm Hg and gauge pressure ranges as low as 0 -5 inches H 2 O 0 -125 mm H 2 0 are available |
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A wide range of materials can be used for the sensing film, from rubber to plastic for low-pressure devices, silicon for medium pressures, to stainless steel for high pressures | Diaphragms: They consist of a thin layer or disk of a material supported on a rigid frame |
As pressure is applied internally through the open end, the increased pressure causes the flattened cross section to become more circulars and the shape to straighten.
C-type bourdon C-type bourdon tubes are used for ranges as low as 0 — 15 psig and as high as 0 — 1500 psig Helical bourdon Helical bourdon tubes are used for ranges as low as 0 — 200 psig up to 0 — 6000 psig Spiral bourdon Very sensitive units are manufactured to measure as low as 0 -10 psig | When pressure is applied to one side of the diaphragm it will deflect |
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The linkage is connected to a pointer or other output device , the tube returns to its original form when the pressure is released | There are three common types of bourdon tubes, the C-shape, the spiral, and the helix |