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Valve monitor and method

  • US 4,821,769 A
  • Filed: 11/12/1986
  • Issued: 04/18/1989
  • Est. Priority Date: 11/12/1986
  • Status: Expired due to Term
First Claim
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1. An apparatus for monitoring operation of a three way valve linking a common conduit to first and second conduits in a fluid system, comprising:

  • second alternating current signals of a first second alternating current signals of a first frequency, said signals being out of phase with one another;

    first excitation coupling means for coupling the first alternating current signal from the signal source means to the fluid in the first conduit so that the first alternating current signal can propagate therealong;

    second excitation coupling means for coupling the second alternating current signal from the signal source means to the fluid in the second conduit so that the second alternating current signal can propagate therealong;

    resultant coupling means for coupling a resultant signal from the fluid in the common conduit, said resultant signal being the superposition of the first alternating current signal, after its propagation to the resultant coupling means, with the second alternating current signal, after its propagation to the resultant coupling means;

    reference means for providing a reference alternating current signal at said first frequency; and

    detector means coupled to the resultant coupling means and to the reference means for comparing the phase of the resultant signal with the phase of the reference signal and producing an output signal therefrom, said output signal being indicative of the state of the three way valve.

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