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Compact metal detector of the balanced induction type

  • US 4,423,377 A
  • Filed: 11/12/1980
  • Issued: 12/27/1983
  • Est. Priority Date: 11/12/1980
  • Status: Expired due to Term
First Claim
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1. A compact metal detector of the balanced induction type comprising:

  • (a) a planar assembly having a perimeter, a transmit coil disposed on said assembly enclosing a planar transmit coil area, a receive coil disposed on said planar assembly enclosing a planar receive coil area, said receive coil area being coplanar with the transmit coil area, and said receive coil being disposed adjacent said transmit coil;

    (b) a planar circuit board having a perimeter substantially corresponding to the perimeter of said planar assembly, said planar circuit board disposed parallel and above said planar assembly such that said entire transmit and receive coil areas are covered by said planar circuit board; and

    (c) circuit means including alternating current components which produce a high level oscillating current in response to signals produced in said receive coil and provide said high level oscillating current to a speaker, said components located on said planar circuit board exterior of said receive coil area such that said high level oscillating current does not induce a corresponding high level oscillating current in said receive coil.

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