An Elementary Theory of the Bourdon Gage

A theory of the Bourdon gage is presented based upon two elements of strain, namely, the bending of the walls in a transverse section through the gage tubing, and a longitudinal extension parallel to the axis of the tubing. Practical formulas are derived for the calculation of the sensitivity and the torque of the Bourdon gage. An estimate is made of the maximum stress. The sensitivity of a very thin-walled gage is shown to be proportional to the inverse first power of the wall thickness. Results of a few measurements show agreement with the theory.