A Bourdon tube is often found in a?

A bourdon tube is a type of curved tube where the inside radius is smaller than the outside radius. As Force = Pressure x Area this means that when a pressure is applied internally to the tube the greater surface area on the outside causes the tube to straighten out. This is connected via a mechanical linkage to dial on the front of the gauge. Your typical industrial pressure gauge is the Bourdon Tube tyep.