US Patent 7331239 Self calibrating dual diaphragm pressure sensor

A pressure sensor having a predetermined chamber dome angle with an electrode. A hole is located in the top to provide pressure readings and the bottom has an input port. A primary diaphragm is coated on both sides with an electrode and an insulator. A secondary diaphragm is coated on the side which faces the primary diaphragm. Offset holes are made in the two diaphragms which permits pressure equalization during self calibration. Both diaphragms are initially energized to seal the gage volume, and then the secondary diaphragm is used to self calibrate using a known pressure.