Bourdon tube pressure gauges are 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 center of the 19th century. Eager is based 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. Consequently, the finish of the tube moves by around two or three millimetres. This deflection is a measure of the pressure. It really is used in a movement, which turns the linear deflection 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. Depending on the geometry, material and material thickness, pressures around 7,000 bar can be realised. Based on the requirement, the pressure elements are constructed with copper alloys, stainless steels or special materials such as Monel.
Note
Economical on Bourdon tube pressure gauges can be found on the WIKA website.g