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Article detection and/or recognition using magnetic devices

  • US 4,940,966 A
  • Filed: 04/10/1989
  • Issued: 07/10/1990
  • Est. Priority Date: 06/08/1987
  • Status: Expired due to Fees
First Claim
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1. A method of recognising and/or detecting an article at a given point in the course of its movement from a first location to a second location, which comprises securing to said article while it is at said first location a magnetic device which comprises a plurality of magnetic elements in a predetermined association (e.g. with predetermine numbers of magnetic elements and with predetermined spacings between said elements), at least one of said magnetic elements being a soft magnetic material with low coercivity, high intrinsic permeability and low or zero magnetostriction, and at least one other of said magnetic elements being a semi-hard magnetic material;

  • subjecting the article carrying said magnetic device to a predetermined interrogating magnetic field at said given point and observing the interaction between the interrogating field and the magnetic device carried by the article;

    deducing from said observed interaction the nature of the article; and

    allowing the article to travel from said given point to said second location;

    said first location being a point of access to an underground pipe system and said given point being a site where said pipe system itself is accessible but where the contents of said pipe system are inaccessible.

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