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Liquid sensing circuit

  • US 5,378,993 A
  • Filed: 12/20/1993
  • Issued: 01/03/1995
  • Est. Priority Date: 12/20/1993
  • Status: Expired due to Term
First Claim
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1. A device for sensing a presence of at least one of the following fluids in a chemical feed tube selected from the group consisting of sanitizer, detergent and rinse agent, said device comprising:

  • an oscillator section for determining an oscillating frequency and for determining a duty cycle at which said device operates;

    at least one frequency shaper connected to said oscillator section, said shaper receiving the oscillating frequency and converting said frequency to a square wave;

    at least one sensitivity element connected to said shaper, said sensitivity element being adjustable for changing the sensitivity of the device;

    at least one sensor element connected to said sensitivity element, said sensor sensing the presence of said at least one of the following fluids in the chemical feed tube selected from the group consisting of sanitizer, detergent and rinse agent, and providing an indication signal representing said sensed fluid;

    at least one comparator connected to said sensitivity element, said comparator receiving said indication signal and comparing said signal to a predetermined sequence signal, said comparator outputting a result signal based on said comparison; and

    at least one output section connected to said comparator, said output section receiving said result signal and changing said signal to a steady direct current signal.

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