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Transient electromagnetic method for detecting irregularies on conductive containers having variations in jacket thickness

  • US 4,929,896 A
  • Filed: 11/21/1989
  • Issued: 05/29/1990
  • Est. Priority Date: 12/29/1988
  • Status: Expired due to Term
First Claim
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1. A method for detecting irregularities on electrically conductive walls of container means, comprising the steps of:

  • (a) providing transmitting antenna means and transmitter means connected with said transmitting antenna means;

    (b) providing receiving antenna means and receiver means connected with said receiving antenna means;

    (c) placing said transmitting antenna means in proximity to that portion of the container means wall which is to be investigated;

    (d) placing said receiving antenna means in proximity to the container means wall portion and in proximity to said transmitting antenna means, said receiving antenna means being separated from said transmitting antenna means;

    (e) providing an abruptly changing current to said transmitting antenna means from said transmitter means so as to induce current into the container means wall portion;

    (f) detecting the presence of and the decay of said induced current in said container means wall portion with said receiving antenna means to produce a received signal, said received signal having an intermediate time range and a late time range, said received signal having a maximum occurring in the intermediate or late time ranges, said received signal having an arrival time which is the time when said maximum occurs;

    (g) examining said received signal to determine the maximum of said received signal and examining the received signal to determine the arrival time of said maximum, said maximum and said arrival time providing an indication of the presence or absence of irregularities in said container means wall portion, wherein the presence of irregularities is indicated by a maximum which is greater than a maximum obtained from an irregularity-free container means wall portion.

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