Bourdon tube pressure gauge ? operating principle

Glamorous will be the most regularly used mechanical pressure measuring instruments. Their pressure element is often referred to as a Bourdon tube: The French engineer Eug�ne Bourdon used this functional principle in the middle of the 19th century. It really is based on an elastic spring, a c-shaped, bent tube with an oval cross-section.
The effect of pressure on a Bourdon tube
When the internal space of the Bourdon tube is pressurised, the cross-section is thus altered towards a circular shape. The hoop stresses which are created in this process increase the radius of the c-shaped tube. Therefore, the finish of the tube moves by around several millimetres. This deflection is really a way of measuring the pressure. It is transferred to a movement, which turns the linear deflection right into a rotary movement and, via a pointer, makes this visible on a scale.
Bourdon tube variants
With the c-shaped bent Bourdon tubes, pressures around 60 bar can be displayed. For higher pressures, helical or spiral-type Bourdon tubes are employed. Depending on the geometry, material and material thickness, pressures around 7,000 bar could be realised. Depending on the requirement, the pressure elements are created from copper alloys, stainless steels or special materials such as Monel.
Note
More info on Bourdon tube pressure gauges can be found on the WIKA website.

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