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Fiber optic liquid sensing system

  • US 5,684,296 A
  • Filed: 06/17/1996
  • Issued: 11/04/1997
  • Est. Priority Date: 06/17/1996
  • Status: Expired due to Fees
First Claim
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1. A system for sensing the presence of a liquid, comprising:

  • a light emitting device operable to emit a light signal of a pre-defined amplitude;

    a transmitting fiber optic strand having a first end connected to said light emitting device and a second end, said transmitting strand being operable to transmit a light signal emitted by said light emitting device and to emit said first light signal through the second end;

    a light sensing device operable to sense a plurality of light signals, each having a particular amplitude, and to derive, from each light signal of said plurality of light signals, a voltage value having a magnitude proportional to a magnitude of each light signal'"'"'s particular amplitude;

    a receiving fiber optic strand having a first end connected to said light sensing device and a second end, said receiving strand being operable to receive said plurality of light signals through the second end;

    an optical sensor comprising;

    a housing having opposed proximal and distal ends and defining a hollow interior of a predetermined cross-sectional size and bounded by a peripheral wall in and through which a plurality of apertures of predetermined size are defined at predetermined locations intermediate to said proximal and distal ends for permitting entry of liquid into the housing interior;

    a ferrule projecting a predetermined extension distance into said housing interior from said housing proximal end and terminating in an end wall disposed in spaced confronting opposition to said housing distal end, said ferrule having a cross-sectional size smaller than said cross-sectional size of the housing interior so as to define a predetermined ferrule spacing between said ferrule and said housing peripheral wall, said ferrule retaining said fiber optic transmitting and receiving strands such that the second end of said transmitting strand and the second end of said receiving strand terminate in the housing at and coincident with said ferrule end wall; and

    a light reflector disposed in the housing interior proximate said distal end at a predetermined reflection distance from said ferrule end wall and oriented for receiving said light signal transmitted from said light source and entering the housing interior from said transmitting strand and for reflecting said received light signal onto the ferrule end wall for transmission of said reflected light signal through said receiving strand to said light sensing device, so that said light sensing device derives a first voltage corresponding to said predefined amplitude of said light signal;

    at least a selected plurality of said reflection distance, said ferrule extension distance, said predetermined aperture locations and said aperture size being selected so that liquid entering the housing interior through said apertures forms a liquid conduit spanningly bridging said ferrule and said reflector and through and within which spanning liquid conduit said light signal entering the housing interior from said transmitting strand and reflected back to said receiving strand is also internally reflected by the liquid conduit such that an amplified reflected light signal transmitted to said light sensing device through said receiving strand has a greater amplitude than said light signal entering the housing through said transmitting strand from said light emitting device so that said light sensing device derives a second voltage corresponding to the greater amplitude of said amplified light signal;

    comparing means, connected to said light sensing device, being operable to store a predefined third voltage, to compare said predefined third voltage to said first voltage and to said second voltage, to assert a first signal when said third voltage is substantially equal to said first voltage, and to assert a second signal otherwise; and

    indicator means, connected to said comparing means, operable to receive said first and said second signals and to indicate a dry condition when said first signal is received, and to indicate a wet condition when said second signal is received.

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