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Liquid level detector using audio frequencies

  • US 5,623,252 A
  • Filed: 05/22/1995
  • Issued: 04/22/1997
  • Est. Priority Date: 05/22/1995
  • Status: Expired due to Fees
First Claim
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1. A liquid level detecting system for detecting a conductive liquid level in a container, comprising:

  • a conductive element having an insulative coating mounted in said container;

    means for applying circuit ground potential to any conductive liquid in said container;

    capacitance between said element and ground changing by a factor of greater than 80;

    1 when said conductive element with its insulative coating becomes immersed in said conductive liquid;

    an oscillator producing an output having an audio frequency;

    a pair of series resistors, said conductive element being connected to a point between said series resistors;

    said oscillator output being fed through said series resistors to an active detector, said oscillator output fed to said active detector having an amplitude inversely proportional to the capacitance between said element and ground;

    wherein said output of said oscillator fed to said active detector drops below a predetermined level when said conductive element becomes immersed in the conductive liquid.

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