Stray Capacitance Compensation for a Capacitive Sensor

A capacitive sensor comprising:

• a first sensor body member comprising a process pressure port and partially defining a first chamber;
• a second sensor body member comprising a reference pressure port and partially defining a second chamber;
• a diaphragm disposed between the first and second body members and displaceable in response to relative changes in pressures within the first and second chambers;
• a sensing electrode disposed through a first opening in one of the body members and cooperating with the diaphragm to form a capacitor exhibiting a total capacitance responsive to a position of the diaphragm and to an environmental effect (CT=CA+CS);
• a reference electrode disposed through a second opening in one of the body members and forming a capacitor exhibiting a total capacitance responsive to the environmental effect and non-responsive to the position of the diaphragm (CS′);
• and
• balancing circuitry comprising the sensing electrode and the reference electrode for generating an output signal (VOUT=Ct−CS′).

A capacitive sensor for measuring a process variable comprising:

• a sensing electrode comprising a sensing electrode post, a sensing electrode insulator for electrically insulating the sensing electrode post from a body of the sensor, and an active electrode area in a capacitive relationship with a diaphragm of the sensor that is responsive to the process variable;
• a reference electrode formed of like materials and dimensions as the sensing electrode but lacking an active electrode area in capacitive relationship with the diaphragm;
• and
• circuitry generating an output signal indicative of the process variable and responsive to a difference between capacitance values of the sensing electrode and the reference electrode.