Capacitive pressure transducer
First Claim
1. An accurate pressure transducer system comprising:
- transducer means including a main variable capacitor and having a diaphragm including a conductive plate for deflecting toward and away from a second conductive plate in response to variations in pressure with the variations in capacitance being slightly non-linear over the desired operating pressure range;
a reference capacitance, said reference capacitance including a principal fixed capacitor, and a small variable correction capacitor having a capacitance which is a minor fraction of that of said main variable capacitor;
means for mounting said small variable compensation capacitor to change its capecitance in response to the variations in pressure applied to said main variable capacitor; and
means for comparing the capacitance of said main variable capacitor and said reference capacitance and for producing an output signal of increased linearity through compensation provided by the variable correction capacitor.
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Accused Products
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.
133 Citations
13 Claims
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1. An accurate pressure transducer system comprising:
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transducer means including a main variable capacitor and having a diaphragm including a conductive plate for deflecting toward and away from a second conductive plate in response to variations in pressure with the variations in capacitance being slightly non-linear over the desired operating pressure range; a reference capacitance, said reference capacitance including a principal fixed capacitor, and a small variable correction capacitor having a capacitance which is a minor fraction of that of said main variable capacitor; means for mounting said small variable compensation capacitor to change its capecitance in response to the variations in pressure applied to said main variable capacitor; and means for comparing the capacitance of said main variable capacitor and said reference capacitance and for producing an output signal of increased linearity through compensation provided by the variable correction capacitor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A pressure transducer system comprising:
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principal pressure sensitive capacitance means for providing a generally linear capacitance vs. pressure characteristic, but with slight departures from linearity; electronic means coupled to said principal capacitance means for producing an output electrical signal which varies substantially in correspondence with the changes in capacitance of said principal capacitance means; and compensating means for reducing said departures from linearity, said compensating means including a small compensating pressure sensitive capacitance means coupled to vary with changes in pressure with said principal pressure sensitive capacitance means, and additional electronic means for utilizing the changes in capacitance of said compensating capacitance means for changing said output electrical signal to reduce said departures from linearity. - View Dependent Claims (11)
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12. An accurate pressure transducer system comprising:
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transducer means including a main variable capacitor having a diaphragm including a conductive plate for deflecting toward and away from a second conductive plate in response to variations in pressure, with the variations in capacitance being slightly non-linear over the desired operating pressure range; a small variable correction capacitor having a capacitance which is a minor fraction of that of said main variable capacitor; and means for mounting said small variable correction capacitor to change its capacitance in response to the variations in pressure applied to said main variable capacitor, by an amount having an order of magnitude corresponding to the departure in linearity of the main variable capacitor. - View Dependent Claims (13)
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Specification