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Method and system for determining the depth of an electrically conductive body in a medium having a known conductivity and a known permeability by measuring phase difference between a primary and secondary magnetic field

  • US 5,119,028 A
  • Filed: 04/26/1990
  • Issued: 06/02/1992
  • Est. Priority Date: 04/26/1990
  • Status: Expired due to Fees
First Claim
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1. A method of determining the depth of an electrically conductive body in a medium having a known conductivity and a known permeability, comprising the steps of:

  • generating a primary magnetic field from an electromagnetic wave transmitting means located a distance apart from said conductive body, said primary magnetic field having a time-varying field strength;

    generating a first signal representing the time-varying field strength of said primary magnetic field;

    transmitting the primary magnetic field from said transmitting means into the medium, wherein the primary magnetic field induces an electric current in the conductive body, and the electric current generates a secondary magnetic field having a time-varying field strength and propagating outward from the conductive body and through the medium;

    sensing the strength of the secondary magnetic field by a receiving means, said receiving means generating a second signal representing the time-varying field strength of said secondary magnetic field;

    conducting said first and second signals to a comparator means;

    the comparator means,processing said first and second signals to obtain a third signal having a value indicating the magnitude of a phase difference between said primary and secondary magnetic fields caused by the primary magnetic field propagating through the medium to the conductive body, and by the secondary magnetic field propagating outward from the conductive body and through the medium; and

    transmitting the third signal to a processor means, the processor meanscalculating the depth of the conductive body in the medium from the third signal and the conductivity and permeability of the medium.

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