Suddenly will be the most regularly 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 center of the 19th century. It really is predicated on an elastic spring, a c-shaped, bent tube having 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 process increase the radius of the c-shaped tube. Because of this, the end 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 right into a rotary movement and, via a pointer, makes this visible on a scale.
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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. Depending on geometry, material and material thickness, pressures up to 7,000 bar could be realised. With regards to the requirement, the pressure elements are made of copper alloys, stainless steels or special materials such as for example Monel.
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More info on Bourdon tube pressure gauges are available on the WIKA website.