Method and apparatus for detecting a dry/wet state of a dual exposed thermistor bead liquid level sensor
First Claim
1. Method of detecting a dry/wet state of a dual thermistor bead sensor over a wide operating temperature range, said method comprising the steps of:
- conducting a first predetermined current through one of the thermistor beads of said sensor;
conducting a second predetermined current through the other of the thermistor beads of said sensor, said second predetermined current being substantially less than said first predetermined current;
measuring a first voltage across said one thermistor bead in response to said first predetermined current and generating a first signal representative thereof;
measuring a second voltage across said other thermistor bead in response to said second predetermined current and generating a second signal representative thereof;
modifying said second signal by an offset and gain to generate a third signal; and
detecting the dry/wet state of said sensor over said wide operating temperature range based on said first and third signals.
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Accused Products
Abstract
A method of detecting a dry/wet state of a dual thermistor bead sensor over a wide operating temperature range comprises the steps of: conducting first and second predetermined currents through one and another of the thermistor beads of the sensor, respectively, the second predetermined current being substantially less than the first predetermined current; measuring a first voltage across the one thermistor bead in response to the first predetermined current and generating a first signal representative thereof; measuring a second voltage across the other thermistor bead in response to the second predetermined current and generating a second signal representative thereof; modifying the second signal by an offset and gain to generate a third signal; and detecting the dry/wet state of the sensor over the wide operating temperature range based on the first and third signals. The first predetermined current is conducted through the one thermistor bead at an average current which renders the one thermistor bead a sense thermistor bead, and the second predetermined current is conducted through the other thermistor bead at an average current which renders the other thermistor bead a reference thermistor bead. Apparatus for implementing this method is also disclosed.
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Citations
38 Claims
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1. Method of detecting a dry/wet state of a dual thermistor bead sensor over a wide operating temperature range, said method comprising the steps of:
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conducting a first predetermined current through one of the thermistor beads of said sensor;
conducting a second predetermined current through the other of the thermistor beads of said sensor, said second predetermined current being substantially less than said first predetermined current;
measuring a first voltage across said one thermistor bead in response to said first predetermined current and generating a first signal representative thereof;
measuring a second voltage across said other thermistor bead in response to said second predetermined current and generating a second signal representative thereof;
modifying said second signal by an offset and gain to generate a third signal; and
detecting the dry/wet state of said sensor over said wide operating temperature range based on said first and third signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. Apparatus for detecting a dry/wet state of a dual thermistor bead sensor over a wide operating temperature range, said apparatus comprising:
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a first circuit coupled to said sensor for conducting a first predetermined current through one of the thermistor beads of said sensor and for conducting a second predetermined current through the other of the thermistor beads of said sensor, said second predetermined current being substantially less than said first predetermined current;
a second circuit coupled to said sensor for measuring a first voltage across said one thermistor bead in response to said first predetermined current and generating a first signal representative thereof;
a third circuit coupled to said sensor for measuring a second voltage across said other thermistor bead in response to said second predetermined current and generating a second signal representative thereof;
a fourth circuit coupled to said third circuit for modifying said second signal by an offset and gain to generate a third signal; and
a fifth circuit for detecting the dry/wet state of said sensor over said wide operating temperature range based on said first and third signals. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. Method of detecting a dry/wet state of a dual thermistor bead sensor over a wide operating temperature range, said method comprising the steps of:
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conducting a first predetermined current through one of the thermistor beads of said sensor;
conducting a second predetermined current through the other of the thermistor beads of said sensor, said second predetermined current being substantially less than said first predetermined current;
measuring a first voltage across said one thermistor bead in response to said first predetermined current and generating a first signal representative thereof;
measuring a second voltage across said other thermistor bead in response to said second predetermined current and generating a second signal representative thereof;
combining the first and second signals to generate a third signal;
generating a reference signal; and
detecting the dry/wet state of said sensor over said wide operating temperature range based on a comparison of said third signal to said reference signal. - View Dependent Claims (32, 33, 34)
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35. Apparatus for detecting a dry/wet state of a dual thermistor bead sensor over a wide operating temperature range, said apparatus comprising:
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a first circuit coupled to said sensor for conducting a first predetermined current through one of the thermistor beads of said sensor and for conducting a second predetermined current through the other of the thermistor beads of said sensor, said second predetermined current being substantially less than said first predetermined current;
a second circuit coupled to said sensor for measuring a first voltage across said one thermistor bead in response to said first predetermined current and generating a first signal representative thereof;
a third circuit coupled to said sensor for measuring a second voltage across said other thermistor bead in response to said second predetermined current and generating a second signal representative thereof;
a fourth circuit coupled to said second and third circuits for combining the first and second signals to generate a third signal; and
a fifth circuit for detecting the dry/wet state of said sensor over said wide operating temperature range based on a comparison of said third signal with a reference signal. - View Dependent Claims (36, 37, 38)
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Specification