Patent ID: 8893555

Claim:
A pressure sensor comprising: a body defining an interior space; a diaphragm dividing the interior space into a measured pressure cavity and a reference pressure cavity; a measured pressure inlet in the body in fluid communication with the measured pressure cavity; a single electrode comprising a plate portion having a face separated from the diaphragm by a gap to form a capacitance there between, and further comprising a post extending from the plate portion through the body; a ceramic seal member disposed between the electrode and the body to provide electrical insulation there between, a first portion of the ceramic seal member being brazed to the body and a second portion of the ceramic seal member being brazed to the electrode to form a hermetic seal there between and to support the plate portion within the reference pressure cavity in a position spaced from the body by a vacuum relief space; the plate portion of the electrode dividing the reference pressure cavity into a front volume adjacent the face and a rear volume behind the plate portion, the front volume and rear volume in fluid communication through the vacuum relief space; and an evacuation opening through the body and into the rear volume, such that a vacuum applied at the evacuation opening will evacuate the rear volume directly and will evacuate the front volume through the vacuum relief space.