Bourdon tube pressure gauge ? operating principle

Bourdon tube pressure gauges are the most regularly used mechanical pressure measuring instruments. Their pressure element is frequently referred to as a Bourdon tube: The French engineer Eug�ne Bourdon used this functional principle in the middle of the 19th century. Lost is based on an elastic spring, a c-shaped, bent tube having an oval cross-section.
The result 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 technique raise the radius of the c-shaped tube. Therefore, Extra of the tube moves by around two or three millimetres. This deflection is really a measure of 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 up to 60 bar can be displayed. For higher pressures, helical or spiral-type Bourdon tubes are used. With respect to the geometry, material and material thickness, pressures up to 7,000 bar can be realised. With regards to the requirement, the pressure elements are created from copper alloys, stainless steels or special materials such as for example Monel.
Note
More info on Bourdon tube pressure gauges can be found on the WIKA website.

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