Studies are the most frequently used mechanical pressure measuring instruments. Great 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 with 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 which are created in this process increase the radius of the c-shaped tube. Due to this fact, the end of the tube moves by around several millimetres. This deflection is really a measure of the pressure. It is transferred to 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 can be displayed. For higher pressures, helical or spiral-type Bourdon tubes are employed. With Elite to the geometry, material and material thickness, pressures around 7,000 bar can be realised. With respect to the requirement, the pressure elements are constructed of copper alloys, stainless steels or special materials such as for example Monel.
Note
Further information on Bourdon tube pressure gauges can be found on the WIKA website.