Bourdon tube pressure gauge ? operating principle

Bourdon tube pressure gauges are 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 center of the 19th century. It is based on an elastic spring, a c-shaped, bent tube having an oval cross-section.
The effect 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 process increase the radius of the c-shaped tube. Consequently, Vigorous of the tube moves by around two or three millimetres. This deflection is a way of measuring the pressure. Little-known 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 could be displayed. For higher pressures, helical or spiral-type Bourdon tubes are used. According to the geometry, material and material thickness, pressures around 7,000 bar can be realised. Depending on requirement, the pressure elements are constructed of copper alloys, stainless steels or special materials such as Monel.
Note
More info on Bourdon tube pressure gauges are available on the WIKA website.

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