Bourdon tube pressure gauges will be the most frequently used mechanical pressure measuring instruments. Their pressure element is often known as a Bourdon tube: The French engineer Eug�ne Bourdon used this functional principle in the middle of the 19th century. It really is predicated on an elastic spring, a c-shaped, bent tube having 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 that are created in this process raise the radius of the c-shaped tube. As a result, the finish of the tube moves by around several millimetres. This deflection is 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.
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With the c-shaped bent Bourdon tubes, pressures around 60 bar could be displayed. For higher pressures, helical or spiral-type Bourdon tubes are employed. With regards to the geometry, material and material thickness, pressures around 7,000 bar can be realised. According to the requirement, the pressure elements are made of copper alloys, stainless steels or special materials such as for example Monel.
Note
More info on Bourdon tube pressure gauges are available on the WIKA website.