Variable-capacitance type sensor and variable-capacitance type sensor system using the same
First Claim
1. A variable-capacitance type sensor system comprising:
- series-connected first and second capacitors, said second capacitor being connected at one end to one end of said first capacitor, and one of said first and second capacitors acting as a pressure-capacitance transducer;
detecting means connected to a connection node between said first and second capacitors, for detecting a terminal voltage of said second capacitor input via said connection node;
a memory connected to an output terminal of said detecting means, for receiving an output of said detecting means in synchronism with a clock signal and storing the same;
an integrator connected between an output terminal of said memory and the other end of said first capacitor, for charging said first and second capacitors which are serially connected according to an output voltage derived by integrating the output of said memory, the output voltage of said integrator varying in inverse proportion to the capacitance of said first capacitor when said first capacitor acts as the transducer, and in proportion to the capacitance of said second capacitor when said second capacitor acts as the transducer; and
a output terminal connected to the output terminal of said integrator, for outputting the output voltage of said integrator.
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Accused Products
Abstract
A constant-capacitance capacitor is series-connected with a variable-capacitance capacitor whose capacitance varies with the pressure. The other end of the variable-capacitance capacitor is connected to the ground potential terminal of a D.C. power source. The terminal voltage of the variable-capacitance capacitor is compared with a threshold voltage provided by the D.C. power source by means of a comparator. An output voltage of the comparator is stored into a memory in synchronism with a clock pulse signal. An output voltage of the memory is integrated by an integrator. An output voltage of the integrator is supplied to a buffer amplifier for lowering the signal source impedance with respect to the output voltage. An output voltage obtained from the buffer amplifier is fed back to the other end of the constant-capacitance capacitor and at the same time supplied to an output terminal.
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Citations
18 Claims
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1. A variable-capacitance type sensor system comprising:
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series-connected first and second capacitors, said second capacitor being connected at one end to one end of said first capacitor, and one of said first and second capacitors acting as a pressure-capacitance transducer; detecting means connected to a connection node between said first and second capacitors, for detecting a terminal voltage of said second capacitor input via said connection node; a memory connected to an output terminal of said detecting means, for receiving an output of said detecting means in synchronism with a clock signal and storing the same; an integrator connected between an output terminal of said memory and the other end of said first capacitor, for charging said first and second capacitors which are serially connected according to an output voltage derived by integrating the output of said memory, the output voltage of said integrator varying in inverse proportion to the capacitance of said first capacitor when said first capacitor acts as the transducer, and in proportion to the capacitance of said second capacitor when said second capacitor acts as the transducer; and a output terminal connected to the output terminal of said integrator, for outputting the output voltage of said integrator. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A variable-capacitance type sensor system comprising:
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first and second capacitors, said second capacitor being connected at one end to one end of said first capacitor; selection means connected between the other ends of said first and second capacitors, for sequentially and periodically completing one of a charging circuit for charging said first capacitor, a parallel circuit for transferring the charge of said first capacitor to said second capacitor, and a discharging circuit for discharging the charge of said first and second capacitors; detecting means connected to the other end of said second capacitor, for detecting a voltage occurring across said first and second capacitors when said parallel circuit of said first and second capacitors is completed by said selection means; a memory connected to an output terminal of said detecting means, for receiving an output of said detecting means in synchronism with a clock signal and storing the same; an integrator connected between an output terminal of said memory and the other end of said first capacitor, for supplying an output voltage derived by integrating the output of said memory to said first capacitor when said charging circuit for said first capacitor is completed by said selection means, the output voltage of said integrator varying one of (a) in proportion to the capacitance of said second capacitor and (b) in inverse proportion to the capacitance of said first capacitor; and an output terminal connected to the output terminal of said integrator, for outputting the output voltage of said integrator. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A variable-capacitance type sensor comprising:
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a planar electrode capacitor which has fixed and movable electrodes with surfaces thereof set to face each other and whose static capacitance varies according to a variation in a distance between the electrodes in a direction perpendicular to the electrodes; and a fixed constant-capacitance capacitor serially connected to the planar electrode capacitor; wherein capacitance of the variable-capacitance type sensor, which varies according to a pressure applied thereto, is a resultant synthesized capacitance of the static capacitance of the planar electrode capacitor and a capacitance of the constant-capacitance capacitor, thus resulting in an improved output characteristic for the variable-capacitance type sensor.
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Specification