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Gradiometer apparatus with compensation coils for measuring magnetic fields

  • US 5,113,136 A
  • Filed: 01/22/1990
  • Issued: 05/12/1992
  • Est. Priority Date: 01/20/1989
  • Status: Expired due to Term
First Claim
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1. An apparatus for measuring a very weak magnetic field such as that generated by a human body, comprising:

  • a gradiometer for sensing the magnetic field;

    a gradiometric field measuring circuit, operatively connected to said gradiometer, for outputting a signal indicative of the magnetic field sensed by said gradiometer;

    at least three compensation coils for detecting uniform magnetic fields existing around said gradiometer, said three compensation coils being oriented in three different directions that are not in parallel with any one plane;

    at least three magnetic field measuring circuits having sensitivity characteristics, operatively connected to said compensation coils, respectively, for outputting signals indicative of the uniform magnetic fields in the three different directions detected by said compensation coils; and

    a magnetic noise eliminating circuit, operatively connected to said gradiometric and magnetic field measuring circuits, for eliminating magnetic noise in the signal indicative of the magnetic field output from said gradiometric field measuring circuit using scalar products of weight vectors containing weight factors predetermined by the sensitivity characteristics of said magnetic field measuring circuits and measured vectors containing, as vector components, magnetic fields previously measured by said magnetic field measuring circuits and said gradiometric field measuring circuit.

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