Bourdon tube pressure gauge ? operating principle

Bourdon tube pressure gauges will be the most frequently used mechanical pressure measuring instruments. Giveaway is frequently referred to as a Bourdon tube: The French engineer Eug�ne Bourdon made use of 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 result of pressure on a Bourdon tube
Once the internal space of the Bourdon tube is pressurised, the cross-section is thus altered towards a circular shape. The hoop stresses that are created in this technique raise the radius of the c-shaped tube. Due to this fact, the finish of the tube moves by around several millimetres. This deflection is really a measure of the pressure. It really is transferred to a movement, which turns the linear deflection into a rotary movement and, with a pointer, makes this visible on a scale.
Bourdon tube variants
With the c-shaped bent Bourdon tubes, pressures around 60 bar could be displayed. For higher pressures, helical or spiral-type Bourdon tubes are used. According to the geometry, material and material thickness, pressures up to 7,000 bar can be realised. Depending on 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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