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Digital liquid level sensing apparatus

  • US 5,406,843 A
  • Filed: 10/27/1993
  • Issued: 04/18/1995
  • Est. Priority Date: 10/27/1993
  • Status: Expired due to Term
First Claim
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1. An apparatus for detecting a fluid level within a fluid reservoir within which a capacitive element array is disposed, wherein the capacitive element array includes a plurality of independent input plates spaced longitudinally along an axis of measurement and a single output plate disposed generally parallel to said input plates and having a length sufficient to span all of said input plates, said apparatus comprising:

  • controller means for sequentially applying an input signal to each one of said input plates sequentially, one at a time, to thereby electrically excite each said input plate;

    current to voltage amplifier means responsive to said output plate for generating a voltage signal representative of the current coupled onto said output plate each time one of said input plates is electrically excited by said controller means;

    peak detector means responsive to said current to voltage amplifier means for generating a peak voltage signal representative of the peak magnitude of the voltage output signal from said current to voltage amplifier means each time one of said input plates is electrically excited by said controller means;

    means for storing each one of said peak voltage signals associated with the current coupled onto to said output plate for each input plate excited by said controller means;

    said controller means including means for comparing said peak voltage output signals generated from the excitation of said input plates, one of said input plates at a time in sequential fashion against a reference value, and for determining the difference in each of said peak voltage output signals from said reference value, to thereby detect a change in the dielectric from any one of said input plates relative to said reference value, to thereby detect a liquid/air interface within said fluid reservoir from which a level of said liquid can be determined.

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