Sensor or capacitance measuring with a microprocessor
First Claim
1. An apparatus for measuring a parameter, the apparatus comprising:
- a microprocessor having a plurality of pins;
a sensor capacitor configured to change capacitance as the parameter changes, the sensor capacitor having a first lead electrically connected to a first pin of the microprocessor, and a second lead electrically connected to a second pin of the microprocessor;
a first reference capacitor having a first lead electrically connected to a third pin of the microprocessor, and a second lead electrically connected to the second pin of the microprocessor;
a resistor having a first lead electrically connected to a fourth pin of the microprocessor, and a second lead electrically connected to the second pin of the microprocessor; and
a second reference capacitor having a first lead electrically connected to a fifth pin of the microprocessor, and a second lead electrically connected to the second pin of the microprocessor.
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Accused Products
Abstract
An apparatus, system, or method for measuring parameters, measuring or determining capacitance, producing a digital output that is dependent upon a capacitance, or converting a variable capacitance output, of a sensor capacitor for example, into a digital format. By activating and deactivating pins, a microprocessor may form various circuits, for instance, each containing a resistor and a different capacitor, in some embodiments, without the use of intermediate switching components. The microprocessor may alternately measure the time to change the charge of each of the capacitors and then calculate the capacitance of one of the capacitors using the measured times and known capacitances of one or more reference capacitors. Certain embodiments use two reference capacitors and alternately charge and discharge the capacitors, and a simple formula may be used to calculate capacitance using times to reach a threshold voltage. A measured parameter may be humidity or pressure, for example.
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Citations
34 Claims
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1. An apparatus for measuring a parameter, the apparatus comprising:
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a microprocessor having a plurality of pins;
a sensor capacitor configured to change capacitance as the parameter changes, the sensor capacitor having a first lead electrically connected to a first pin of the microprocessor, and a second lead electrically connected to a second pin of the microprocessor;
a first reference capacitor having a first lead electrically connected to a third pin of the microprocessor, and a second lead electrically connected to the second pin of the microprocessor;
a resistor having a first lead electrically connected to a fourth pin of the microprocessor, and a second lead electrically connected to the second pin of the microprocessor; and
a second reference capacitor having a first lead electrically connected to a fifth pin of the microprocessor, and a second lead electrically connected to the second pin of the microprocessor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of measuring the capacitance of a first capacitor, the method comprising in any order except where order is indicated, at least the steps of:
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activating at least a first pin of a microprocessor, wherein the first pin is electrically connected to the first capacitor;
while the first pin is activated, measuring a time to change the charge of the first capacitor;
after the measuring of the time to change the charge of the first capacitor, deactivating the first pin into a high impedance state;
activating at least a second pin of the microprocessor, wherein the second pin is electrically connected to a second capacitor;
while the second pin is activated, measuring a time to change the charge of the second capacitor;
after the measuring of the time to change the charge of the second capacitor, deactivating the second pin into a high impedance state;
activating at least a third pin of the microprocessor, wherein the third pin is electrically connected to a third capacitor;
while the third pin is activated, measuring a time to change the charge of the third capacitor;
after the measuring of the time to change the charge of the third capacitor, deactivating the third pin into a high impedance state;
using at least the time to change the charge of the first capacitor, the time to change the charge of the second capacitor, and the time to change the charge of the third capacitor, calculating the capacitance of the first capacitor. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
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23. An apparatus for determining the capacitance of a sensor capacitor, the apparatus comprising:
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a first reference capacitor;
a voltage comparator;
a timer; and
a microprocessor comprising;
a first pin electrically connected to the sensor capacitor, wherein the microprocessor is configured to activate the first pin as an output and drive the first pin to a first voltage, the microprocessor is configured to activate the first pin as an output and drive the first pin to a second voltage, and the microprocessor is configured to deactivate the first pin into a high-impedance state, a second pin electrically connected to the first reference capacitor, wherein the microprocessor is configured to activate the second pin as an output and drive the second pin to the first voltage, the microprocessor is configured to activate the second pin as an output and drive the second pin to the second voltage, and the microprocessor is configured to deactivate the second pin into a high-impedance state, at least one third pin electrically connected to at least one of the sensor capacitor and the first reference capacitor, wherein the microprocessor is configured to activate at least one third pin as an output and drive the at least one third pin to the first voltage, the microprocessor is configured to activate at least one third pin as an output and drive the at least one third pin to the second voltage, and the microprocessor is configured to activate at least one third pin as an input to the comparator;
wherein the microprocessor is configured to use the timer to measure a first time for the sensor capacitor to change from the first voltage to a first threshold voltage, the microprocessor is configured to use the timer to measure a second time for the first reference capacitor to change from the first voltage to the first threshold voltage, and the microprocessor is configured to use at least the first time, the second time, and a capacitance of the first reference capacitor to calculate a capacitance of the sensor capacitor. - View Dependent Claims (24, 25, 26, 27)
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28. An apparatus for producing a digital output that is dependent upon a capacitance of a sensor capacitor, the apparatus comprising:
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a microprocessor having a plurality of pins;
a sensor capacitor having a first lead electrically connected to a first pin of the microprocessor, and a second lead electrically connected to at least one common pin of the microprocessor;
a first reference capacitor having a first lead electrically connected to a second pin of the microprocessor, and a second lead electrically connected to at least one common pin of the microprocessor; and
a resistor having a first lead electrically connected to a third pin of the microprocessor, and a second lead electrically connected to at least one common pin of the microprocessor; and
wherein the microprocessor is configured to;
activate the first pin and at least one common pin as voltage outputs to apply a first voltage across the sensor capacitor;
activate the third pin as a voltage output to establish a first current through the resistor;
deactivate at least one common pin as a voltage output;
activate at least one common pin as a comparator input;
measure the time for a voltage across the sensor capacitor to reach a threshold voltage using the comparator input;
deactivate the first pin to a high-impedance state;
activate the second pin and at least one common pin as voltage outputs to apply the first voltage across the first reference capacitor;
activate the third pin as a voltage output to establish the first current through the resistor;
deactivate at least one common pin as a voltage output;
activate at least one common pin as a comparator input;
measure the time for the voltage across the first reference capacitor to reach the threshold voltage using the comparator input;
deactivate the second pin to a high-impedance state; and
calculate a digital output that is dependent upon the capacitance of the sensor capacitor using at least the time for the voltage across the sensor capacitor to reach the threshold voltage and the time for the voltage across the first reference capacitor to reach the threshold voltage. - View Dependent Claims (29)
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30. A method of converting the variable capacitance output of a sensor capacitor into a digital format, the method comprising in any order at least the steps of:
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using a microprocessor, without the use of intermediate switching components, forming a circuit to facilitate changing the charge of the sensor capacitor;
using the microprocessor, without the use of intermediate switching components, changing the charge of the sensor capacitor while measuring the time required to change the charge of the sensor capacitor;
using the microprocessor, without the use of intermediate switching components, reconfiguring the circuit to facilitate changing the charge of a first reference capacitor;
using the microprocessor, without the use of intermediate switching components, changing the charge of the first reference capacitor while measuring the time required to change the charge of the first reference capacitor;
using the microprocessor, without the use of intermediate switching components, reconfiguring the circuit to facilitate changing the charge of a second reference capacitor;
using the microprocessor, without the use of intermediate switching components, changing the charge of the second reference capacitor while measuring the time required to change the charge of the second reference capacitor; and
using the microprocessor and at least the time required to change the charge of the sensor capacitor, the time required to change the charge of the first reference capacitor, and the time required to change the charge of the second reference capacitor, calculating a digital output that is dependent upon the capacitance of the sensor capacitor. - View Dependent Claims (31, 32, 33, 34)
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Specification