Basic principle of Elastic diaphragm gauges:
when an elastic transducer (diaphragm is this case) is subjected to a pressure, it deflects. This deflection is proportional to the applied pressure when calibrated.
Description of Elastic diaphragm gauges:
The main parts of the diaphragm which is a thin circular plate (made of springy metal) is fixed firmly around its edges. The diaphragm may either be flat or corrugated.