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Method for excitation and detection of magnetic elements by a mechanical resonance

  • US 5,760,580 A
  • Filed: 12/16/1996
  • Issued: 06/02/1998
  • Est. Priority Date: 04/26/1994
  • Status: Expired due to Fees
First Claim
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1. A method for detecting a magnetic element in an interrogation zone, the magnetic or mechanical properties of the magnetic element being affectable by an external magnetic field, the method comprising:

  • generating an excitation signal for a first coordinate axis in the interrogation zone by at least two excitation means located at a distance from each other, so that a symmetry plane for the excitation signal is obtained between the excitation means;

    placing the magnetic element between one of the at least two excitation means and the symmetry plane;

    magnetically exciting a mechanical resonance in the magnetic element so as to generate a magnetic signal arising from the mechanical oscillation;

    detecting the magnetic signal symmetrically at both sides of the symmetry plane by two detectors arranged at different sides of the symmetry plane; and

    generating a difference signal from the signals detected by the detectors;

    whereby the difference signal thus generated contains a magnetic signal caused by resonance oscillation of the magnetic element, but substantially lacks a component caused by the excitation signal.

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