A diaphragm seal is a device in which a flexible membrane (diaphragm)seals and isolates the measuring instrument from the process medium. The instrument side of the diaphragm is filled with appropriate fluid. The pressure exerted by the process fluid on the Diaphragm is hydraulically transmitted through the seal fluid to be the pressure sensing element. Diaphragm seal protects the pressure sensor from the harmful and hazardous effect the process fluid.