Bourdon Tube

The Bourdon tube is a fundamental sensing element in mechanical pressure gauges, consisting of a flattened, C-shaped or helical tube made from elastic materials. When internal pressure increases, the tube tends to straighten due to its cross-sectional geometry, creating proportional mechanical displacement at the sealed tip. This displacement is mechanically amplified through linkages to rotate a pointer on a calibrated dial, providing visual pressure readings. Bourdon tubes operate on the principle that pressure applied to the inside of a curved tube with non-circular cross-section causes it to deform toward a circular shape, generating measurable motion.

Pressure applied inside a curved tube with elliptical or flattened cross-section causes the tube to straighten as it attempts to achieve a circular cross-section. This elastic deformation creates proportional mechanical displacement at the free end, which is transmitted through linkages to move a pointer across a calibrated scale.