This is a circular membrane elastic sensitive element. When both sides of the diaphragm is the effect of different pressure (or power), the diaphragm move to low pressure side of the strain, the center temperature and pressure difference into a certain relationship of displacement. Diaphragm are mainly in the form of flat diaphragm, hanging chain, diaphragm and corrugated diaphragm . Flat diaphragm and according to whether the fixed support, center around whether to open hole and the regional difference of stress distribution of diaphragm is divided into a variety of forms, one of the most commonly used is composed of fixed cross section such as circular thin plate around the flat diaphragm. Hanging chain diaphragm consists of circular plate near the edge slot, the edge of the elastic strain mainly occurred in the circular groove, commonly used to achieve the diaphragm compression strain tube or column pressure. Hanging chain hard center part of the diaphragm in compression moves close to the translation, so used in capacitive sensors or piezoelectric sensor effect is better. Corrugated diaphragm pressure has a circular concentric ripples. In order to increase the displacement of the diaphragm center can make two diaphragm welded together into the bellows or further to several bellows concatenated as bellows.