How does bourdon tube gauge work?

A Bourdon gauge consists of a C-shaped pipe with one end closed and the other end attached to a chamber whose pressure is being measured. When there is a pressure difference between the inside of the pipe and the outside, there will be a net force acting on the C-shaped pipe which will either try to curl the pipe into a tighter C shape (if the pressure in the pipe is less than the ambient air pressure), or the force will tend to straighten out the pipe (if the pressure is higher inside). This force can be measured, and from the measurement of this force, the gauge pressure within the pipe can be calculated.