[161] Bourdon-tube pressure gauge
Most pressure gauges operate on the principle of a Bourdon tube. When hydraulic fluid flows into the tube, an identical pressure is produced throughout. Due to the difference in area between the outer and inner curved surfaces, the tube is bent. This movement is transferred to a pointer.
This type of gauge is not protected against overload. A cushioning restrictor must be installed in the inlet connection prevent pressure surges from damaging the tube.