The Bourdon Tube is a nonliquid pressure measurement device. It is widely used in applications where inexpensive static pressure measurements are needed.
A typical Bourdon tube contains a curved tube that is open to external pressure input on one end and is coupled mechanically to an indicating needle on the other end, as shown schematically below.
Typical Bourdon Tube Pressure Gages
The external pressure is guided into the tube and causes it to flex, resulting in a change in curvature of the tube. These curvature changes are linked to the dial indicator for a number readout. Alternatively, a strain gage circuit can be attached on the tube to convert the pressure-induced deflections into electric voltage signals. These signals can then be output electronically, rather than mechanically with the dial indicator.