Bourdon tube pressure gauges are the most frequently used mechanical pressure measuring instruments. Their pressure element is frequently referred to as a Bourdon tube: The French engineer Eug�ne Bourdon made use of this functional principle in the center of the 19th century. It is based on an elastic spring, a c-shaped, bent tube with an oval cross-section.
The result 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. Therefore, Playful of the tube moves by around several millimetres. This deflection is a way of measuring the pressure. It really is transferred to a movement, which turns the linear deflection right 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 up to 60 bar could be displayed. For higher pressures, helical or spiral-type Bourdon tubes are employed. According to the geometry, material and material thickness, pressures up to 7,000 bar could be realised. With respect to the requirement, the pressure elements are created from copper alloys, stainless steels or special materials such as Monel.
Note
More info on Bourdon tube pressure gauges can be found on the WIKA website.