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Adaptive thresholding for metal detection

  • US 5,600,942 A
  • Filed: 03/31/1995
  • Issued: 02/11/1997
  • Est. Priority Date: 03/31/1995
  • Status: Expired due to Term
First Claim
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1. A metal detector system for detecting the passage of metal objects through a magnetic detection field, said metal detector system including at least one channel comprising a detection coil disposed in said magnetic detection field and a detection circuit for producing a channel output signal having a noise component therein, said channel output signal including a detection component upon the passage of a ferrous metal object through said magnetic detection field;

  • means for sampling said channel output signal and producing digitized channel signals, means for comparing said digitized channel signals with positive and negative adaptive thresholds and producing an output indication when one of said digitized channel signals exceeds either said positive or said negative adaptive threshold, and means for producing positive and negative peak averages and independently setting said positive and negative adaptive thresholds according to the positive peak average and the negative peak average, respectively, of said noise component.

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