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Liquid level sensing circuitry

  • US 4,385,290 A
  • Filed: 08/25/1981
  • Issued: 05/24/1983
  • Est. Priority Date: 08/25/1981
  • Status: Expired due to Fees
First Claim
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1. Liquid level sensing circuitry adapted for energization from a d.c. power source including:

  • a first circuit portion having a conductive probe adapted for connection to the d.c. source for providing a first signal at said conductive probe when the liquid is not in contact with said conductive probe and providing a second signal when the liquid sensed is in contact with said conductive probe;

    a second circuit portion operatively connected to said first circuit portion and including a switched electrical power conductor for controlling the application of d.c. power to said second circuit portion and a control point for providing a first state for said control point independent of said first circuit portion upon completion of a time period following the application of d.c. power to said second circuit portion via said switched electrical power conductor and for providing a second state for said control point provided said second signal is present for a period of time following the removal of d.c. power to said second circuit portion via said switched electrical power conductor; and

    a third circuit portion operatively connected to said second circuit portion and said switched electrical power conductor of said second circuit portion and having a first discernible indicator for providing a first discernible indication in response to said first state of said control point if present after a period of time following termination of d.c. power to said second circuit portion via said switched electrical power conductor plus subsequent supply of d.c. power via said switched electrical power conductor and a second discernible indicator for providing a second discernible indication in response to said second state at said control point and the supply of d.c. power via said switched electrical power conductor.

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