Abstract: A capacitive pressure transducer system includes a reference capacitor and a capacitor which varies with pressure; and circuitry which involves alternately charging one of the capacitors to a reference voltage level, and then switching to charge the other capacitor; and circuitry for producing an output voltage which varies as the duty cycles of the two capacitors shift; and the output is therefore substantially proportional to the pressure changes. Feedback is provided to incrementally change the capacitor charging and switching timing or duty cycles by changing the charging current or the reference voltage at which switching occurs, to substantially eliminate deviations from linearity in the voltage versus pressure characteristic.

Abstract: Two square plates of ordinary inexpensive soda lime glass are spaced apart from one another, and are sealed together by a ring of glass frit, with the two plates overlying one another, but with the corners of the two plates displaced so that the corners of each of the two plates extend past the sides of the other plates. The plates may be spaced apart by a small distance, for example, from about 1/2 to several thousandths of an inch, and thin conductive layers on the two facing surfaces form a variable capacitor which changes in capacitance when pressure is applied to the outside of the two plates. Connections for the conductive plates extend out to the corners of the plates beyond the sides of the other plate to permit easy access. Electrical connections are made through the use of elongated conductive rubber elements.

Abstract: A highly linear capacitive pressure transducer system includes one or more conductive plates mounted on a diaphragm for deflection toward and away from another conducting plate. The opposed conductive plates include both a main variable capacitor and a small separate compensation capacitor mounted on the same structure. The small compensation capacitor is connected in parallel with a larger fixed reference capacitor. The outputs from the main variable capacitor, and from the reference capacitance including the fixed capacitor and the small variable capacitor, are compared in electronic circuitry which produces an output signal proportional to the variations in pressure applied to the diaphragm. When the small variable capacitor has a change in capacitance with pressure generally of the same order of magnitude as the deviations from linearity of the main variable capacitor, the linearity of the output signal with changes in pressure is significantly increased.