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US 6,549,136 B2Granted
Sensing and switching circuit employing a positive-temperature-coefficient sensing device
AssigneeLansense, LLC
InventorDonald G. Landis
Life of this patent
Estimating the term…
Abstract
A sensor and associated circuitry for sensing and reacting to the presence of a fluid or other material having heat capacity. A positive-temperature-coefficient device initiates a switching step when the amount of heat-capacity material reaches a certain level, or is totally absent. The switching step may trigger an alarm or control circuit to rectify the fluid level.
Claims27
A sensing and switching circuit comprising:
- (a) a body of positive-temperature-coefficient material having a first conductive coating on a first surface thereof and a second conductive coating on a second surface thereof, said second conductive coating being divided into a first zone and a second zone which are not in direct electrical contact with each other,
- (b) a source of first electric potential connectable to said first conductive coating,
- (c) first resistive means for connecting said first zone of said second conductive coating to a source of second electric potential different from said first electric potential, said first resistive means having first and second terminals and a node intermediate said first and second terminals,
- (d) second resistive means for connecting said second zone of said second conductive coating to a source of electric potential different from said first electric potential,
- (e) first switching means for connecting said source of first electric potential to said first conductive coating,
- (f) means for thermally coupling said first zone of said second conductive coating, and the portion of said body of positive-temperature-coefficient material proximate thereto, to a heat receptor, and
- (g) output switching means coupled to said node.
4 more elements
A fluid detector comprising:
- (a) a conduit for said fluid,
- (b) a thermally-conductive ring at least partially encircling said conduit,
- (c) a body of positive-temperature-coefficient material having a first conductive coating on a first surface thereof and a second conductive coating on a second surface thereof, said second conductive coating being divided into a first zone and a second zone which are not in direct electrical contact with each other,
- (d) said first zone of said second conductive coating being in contact with said thermally-conductive ring,
- (e) said second zone of said second conductive coating being in contact with said conduit at a point displaced from said ring along the axis of said conduit,
- (f) first resistive means, having two terminals and a node intermediate its terminals, for connecting said first zone of said second conductive coating to ground,
- (g) second resistive means for connecting said second zone of said second conductive coating to ground, and
- (h) means for electrically energizing said first conductive coating.
5 more elements
A sensing and switching circuit for an inductive load comprising:
- (a) a body of positive-temperature-coefficient material having a first conductive coating on a first surface thereof and a second conductive coating on a second surface thereof, said second conductive coating being divided into a first zone and a second zone,
- (b) a source of first electric potential connectable through said inductive load to said first conductive coating,
- (c) resistive means having first and second terminals for connecting said first zone and said second zone of said second conductive coating to a reference potential different from said first electric potential,
- (d) first switching means for closing the electrical path from said source of first electric potential through said inductive load, said body of positive-temperature-coefficient material, and said resistive means to said reference potential different from said first electric potential, and
- (e) output switching means connected between said first and second terminals of said resistive means.
2 more elements
A method for sensing and announcing the presence of a fluid in contact with a heat-conductive structure which comprises the steps of:
- (a) providing in thermal contact with said heat-conductive structure a body of positive-temperature-coefficient material having on its first surface a first conductive coating and on its second surface a second conductive coating divided into a first zone and a second zone, only the first zone being in thermal contact with said heat-conductive structure,
- (b) electrically energizing said first conductive coating,
- (c) sensing the voltage across at least a portion of a first resistance connected between ground and said first zone of said second conductive coating,
- (d) feeding said sensed voltage to a switching device adapted to turn on in response to a predetermined level of positive voltage,
- (e) recording the instant of time when said switching device turns off,
- (f) measuring the elapsed time between turn-on and turn-off of said switching device,
- (g) periodically repeating steps (b) through (f) until an occurrence when said elapsed time between turn-on and turn-off increases, and
- (h) noting the time of said occurrence as the time of appearance of fluid in contact with said heat-conductive structure.
5 more elements
Dependencies are inferred from the claim text.