Abstract: Inherent capacitive-type nonlinearities in a capacitive displacement transducer can be eliminated or reduced by the introduction of an oppositely-sensed nonlinearity. The oppositely sensed nonlinearity is introduced by selecting a diaphragm thickness to define a stiffness such that there is an increased resistance to deflection. The increased resistance to deflection generates a nonlinearity which decreases with increasing input to offset an oppositely sensed inherent nonlinearly which increases with increasing input, thereby balancing the nonlinearities and achieving an overall linear output.

Abstract: A method and means for determining the deflection of a movable element in a transducer by measurement of capacitance. The result is independent of extraneous capacitance between the transducer terminals and the environment, of the magnitude of the transducer capacitance, and of scaling factors within the measurement circuits. The difference and sum of differential capacitances are determined, preferably independently of their individual values, using switching techniques and a common measurement circuit. The ratio of differential capacitances is determined by causing the measurement signal for one capacitance to be inversely proportional to the magnitude of the other capacitance.

Abstract: A method and apparatus for determining the extent of deflections of a movable diaphragm in a capacitive displacement type transducer. The transducer circuit is connected to a three terminal capacitive type transducer, and produces an output which is essentially of stray capacitances, circuit component tolerances and changes, and dimensional changes in the transducer elements caused by temperature changes. This is achieved by providing an output which is representative of the difference in the capacitances of the two transducer capacitors, nominalized by dividing by the sum of the capacitance reciprocals. The output of the transducer circuit thus represents the extent of the diaphragm deflection with all other transducer and circuit parameter variations removed.

Abstract: A miniature transducer having an ultrathin tensioned silicon diaphragm so as to be responsive to extremely small changes in pressure. A silicon wafer is masked to define diaphragm areas, and etched to form a setback or capacitor gap a predefined depth. The mask is removed, and the entire silicon wafer is etched a second time to achieve the desired diaphragm thickness. The first and second etches are carried out independently, and thus the capacitor gap and diaphragm thickness can be independently formed. Mask and metallizing steps are carried out on glass wafers, and sandwiched around the processed semiconductor wafer, whereupon a large number of the miniature transducers are fabricated simultaneously. Unique patterning, etching and metallizing steps carried out on the sandwich structure allow a number of quadrature unit cells to be formed, thereby maximizing the area of the semiconductor and glass structures.

Abstract: Displacement of a movable transducer element is measured by exciting a capacitive gap (preferably differential capacitive gaps) with triangular waves of voltage to obtain a square current wave output into a zero input impedance amplifier. The square wave output is amplified and synchronously detected to produce a d.c. output signal proportional to displacement. The d.c. output signal is fed back to force rebalance electrodes to electrostatically rebalance the movable transducer element. The feedback signal is a measure of the force being transduced. Initial offsets in the position of the transducer element and capacitances of the capacitive gaps are compensated by signals derived from the capacitive gap excitation waveforms.

Abstract: A checkweigher uses a strain gauge load cell to provide a digital count which in turn is utilized to provide for automatic rezeroing and simplified referencing. The "grey zone" is taken into account for 100% rejection. Give away weight and standard deviation are also automatically determined.