Bourdon tube pressure gauge ? operating principle

Bourdon tube pressure gauges 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 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.
Never 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 that are created in this process increase the radius of the c-shaped tube. Subsequently, the finish of the tube moves by around two or three millimetres. This deflection is really a way of measuring the pressure. It is used in 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 can be displayed. For higher pressures, helical or spiral-type Bourdon tubes are employed. With respect to the geometry, material and material thickness, pressures up to 7,000 bar could be realised. According to the requirement, the pressure elements are made 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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