Capacitive Measurement Multiplexing Circuit and Method
First Claim
1. A system for determining capacitance of a capacitor, comprising:
- at least one first capacitor having a capacitance to be sensed, each at least one first capacitor having a first terminal and a second terminal;
a signal generator coupled to the first terminal of the at least one first capacitor for generating an alternating signal;
a second capacitor having a first terminal coupled to the signal generator and a second terminal;
conversion circuitry for sensing an alternating current at an input thereof and generating a substantially DC voltage output signal based upon the sensed alternating current; and
switching circuitry, coupled between the input of the conversion circuitry and the second terminal of each of the at least one first capacitor and the second capacitor, for selectively coupling the second terminal of the at least one first capacitor and the second capacitor, one at a time, to the input of the conversion circuitry while the second terminal not coupled to the input of the conversion circuitry is coupled to a ground reference, the substantially DC voltage output signal of the conversion circuitry being based upon a capacitance of the capacitor coupled to the input of the conversion circuitry.
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Accused Products
Abstract
A capacitance measuring system, including: a calibration capacitor; first circuitry for sensing an input current at an input thereof and generating an output signal that is based upon a capacitance appearing at the input of the first circuitry; and multiplexer circuitry, coupled between the input of the first circuitry and a terminal of each of the capacitor to be measured and the calibration capacitor, for selectively coupling the terminal of each, one at a time, to the input of the first circuitry while the terminal not coupled to the input of the conversion circuitry is coupled to a ground reference; and controller circuitry for calculating a capacitance of the capacitor to be measured based upon the output signal of the first circuitry when the capacitor to be measured is coupled to the input thereof and upon the output signal of the first circuitry when the calibration capacitor is coupled to the input thereof.
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Citations
15 Claims
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1. A system for determining capacitance of a capacitor, comprising:
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at least one first capacitor having a capacitance to be sensed, each at least one first capacitor having a first terminal and a second terminal; a signal generator coupled to the first terminal of the at least one first capacitor for generating an alternating signal; a second capacitor having a first terminal coupled to the signal generator and a second terminal; conversion circuitry for sensing an alternating current at an input thereof and generating a substantially DC voltage output signal based upon the sensed alternating current; and switching circuitry, coupled between the input of the conversion circuitry and the second terminal of each of the at least one first capacitor and the second capacitor, for selectively coupling the second terminal of the at least one first capacitor and the second capacitor, one at a time, to the input of the conversion circuitry while the second terminal not coupled to the input of the conversion circuitry is coupled to a ground reference, the substantially DC voltage output signal of the conversion circuitry being based upon a capacitance of the capacitor coupled to the input of the conversion circuitry. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A system for determining the capacitance of a capacitor, comprising:
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at least one first capacitor having a capacitance to be sensed, each at least one first capacitor having a first terminal and a second terminal; a second capacitor having a first terminal and a second terminal; first circuitry for sensing an input current at an input thereof and generating an output signal that is based upon a capacitance appearing at the input of the first circuitry; multiplexer circuitry, coupled between the input of the first circuitry and the second terminal of each of the at least one first capacitor and the second capacitor, for selectively coupling the second terminal of the at least one first capacitor and the second capacitor, one at a time, to the input of the first circuitry while the second terminal not coupled to the input of the conversion circuitry is coupled to a ground reference; and controller circuitry for calculating a capacitance of the at least one first capacitor based upon the output signal of the first circuitry when the at least one first capacitor is coupled to the input thereof and upon the output signal of the first circuitry when the second capacitor is coupled to the input thereof. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification