Abstract: A pressure sensor (40) useful as a vacuum manometer. A reference pressure cavity (50) of the sensor is evacuated through an evacuation opening (72) located behind a plate portion (54) of the sensor electrode (52) having a non-planar surface for supporting the diaphragm (44) during an overpressure event. The electrode is hermetically sealed to the body (42) of the sensor by a brazed joint with a ceramic seal member (60) disposed there between. The brazed joint may include a layer of buffer material (79) which provides a degree of malleability to the joint to avoid cracking of the ceramic seal member. The brazed ceramic/metal joint permits the selection of materials such that differential thermal expansion effects can be passively minimized. The electrode is connected to the sensor circuitry (84) by a wire having a spring section (53), thereby providing a stress free interconnection.

Abstract: A pressure sensor (40) useful as a vacuum manometer. A reference pressure cavity (50) of the sensor is evacuated through an evacuation opening (72) located behind a plate portion (54) of the sensor electrode (52) having a non-planar surface for supporting the diaphragm (44) during an overpressure event. The electrode is hermetically sealed to the body (42) of the sensor by a brazed joint with a ceramic seal member (60) disposed there between. The brazed joint may include a layer of buffer material (79) which provides a degree of malleability to the joint to avoid cracking of the ceramic seal member. The brazed ceramic/metal joint permits the selection of materials such that differential thermal expansion effects can be passively minimized. The electrode is connected to the sensor circuitry (84) by a wire having a spring section (53), thereby providing a stress free interconnection.

Abstract: A capacitive sensor (10) producing an output signal (VOUT) that is insensitive to stray capacitance (CS) caused by environmental and aging conditions. The sensor includes a sensing electrode (11) that exhibits a total capacitance that is responsive to both the measured process variable and to stray capacitance (CT=CA+CS). The sensor also includes a reference electrode (19) that exhibits a stray capacitance (CS?) essentially the same as that of the sensing electrode, but that is insensitive to the process variable. Balancing circuitry (29) provides an output signal that is responsive to the measured process variable and insensitive to the stray capacitance (VOUT=CT?CS?). The reference electrode is manufactured of the same materials and dimensions as the sensing electrode and may be mounted in the sensor body proximate the sensing electrode.