Multiple function stable sensor circuitry
First Claim
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1. A multiple function multiplex, sensor system comprising:
- a reference capacitor;
a pressure sensitive variable capacitor;
a reference current source;
a current source for supplying current which is variable with temperature;
circuitry for applying current to said reference capacitor from said reference current source until a predetermined reference voltage is reached;
circuitry for applying current to said pressure sensitive capacitor from said reference current source until a predetermined reference voltage is reached;
circuitry for alternately supplying current to said capacitors using the reference current source and using the temperature variable current source;
circuitry for determining a first ratio between the time for charging the pressure variable capacitor, and the time for charging the reference capacitor, to provide an indication of the applied pressure; and
said system including circuitry for determining a second ratio of (1) the time required for charging both the reference and pressure variable capacitors using the temperature variable current source, and (2) the time required for charging both capacitors using the reference current source.
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Abstract
Multiple function stable circuitry measures both pressure and temperature for example. It includes both a pressure sensitive capacitor, and fixed reference capacitor, and also includes both a constant current source and a temperature variable current source. The complete cycle includes at least two phases, with one phase of the cycle utilizing one reference capacitor and one pressure variable capacitor; and at least one other phase including the reference capacitor and at least one temperature variable charging source. Other multiple slope multiple functions may also be implemented.
12 Citations
20 Claims
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1. A multiple function multiplex, sensor system comprising:
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a reference capacitor;
a pressure sensitive variable capacitor;
a reference current source;
a current source for supplying current which is variable with temperature;
circuitry for applying current to said reference capacitor from said reference current source until a predetermined reference voltage is reached;
circuitry for applying current to said pressure sensitive capacitor from said reference current source until a predetermined reference voltage is reached;
circuitry for alternately supplying current to said capacitors using the reference current source and using the temperature variable current source;
circuitry for determining a first ratio between the time for charging the pressure variable capacitor, and the time for charging the reference capacitor, to provide an indication of the applied pressure; and
said system including circuitry for determining a second ratio of (1) the time required for charging both the reference and pressure variable capacitors using the temperature variable current source, and (2) the time required for charging both capacitors using the reference current source. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A multiple function multiplex, sensor system comprising:
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a reference capacitor;
a pressure sensitive variable capacitor;
a reference current source;
a current source for supplying current which is variable with temperature;
circuitry for applying current to said reference capacitor from said reference current source until a predetermined reference voltage is reached;
circuitry for applying current to said pressure sensitive capacitor from said reference current source until a predetermined reference voltage is reached;
circuitry for alternately supplying current to said capacitors using the reference current source and using the temperature variable current source;
a source of clock pulse signals;
circuitry for determining the ratio of the number of clock pulses occurring during charging said reference capacitor to the number of clock pulses occurring during charging said pressure sensitive capacitor, to provide an indication of pressure;
circuitry for counting the number of clock pulses occurring during charging the reference capacitor and the pressure sensitive capacitor using first the reference current source, and secondly using the temperature varying current source; and
for using the ratio of these counts to provide an indication of temperature. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A multiple function multiplex, sensor system comprising:
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a reference capacitor;
a pressure sensitive variable capacitor;
a reference current source;
a current source for supplying current which is variable with temperature;
circuitry for applying current to said reference capacitor from said reference current source until a predetermined reference voltage is reached;
circuitry for applying current to said pressure sensitive capacitor from said reference current source until a predetermined reference voltage is reached;
circuitry for alternately supplying current to said capacitors using the reference current source and using the temperature variable current source;
a source of clock pulse signals;
circuitry for determining the ratio defining a first ratio of the number of clock pulses occurring during charging said reference capacitor to the number of clock pulses occurring during charging said pressure sensitive capacitor, to provide an indication of pressure;
circuitry for counting the number of clock pulses occurring during charging the reference capacitor and the pressure sensitive capacitor using first the reference current source, and secondly using the temperature varying current source; and
for using the ratio of these counts defining a second ratio to provide an indication of temperature.said system including circuitry for providing pulse width modulated signals including the components of first ratio. - View Dependent Claims (18, 19, 20)
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Specification