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Self-adjusting inductive object-presence detector

  • US 4,491,841 A
  • Filed: 09/14/1983
  • Issued: 01/01/1985
  • Est. Priority Date: 04/03/1981
  • Status: Expired due to Term
First Claim
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1. A method of detecting the arrival of an object in the vicinity of a sensing element sensitive to such object and subject to ambient change, comprising:

  • sampling the state of the element at successive occasions to obtain sample values dependent on the state of the element;

    establishing at a first rate a first succession of sample values each being superseded by the next as a reference value;

    establishing at a second rate greater than the first rate a second succesion of sample values and comparing each of these sample values with the existing reference value, andindicating the presence of an object in the vicinity of the loop upon the difference between the existing reference value and a sample value of the second succession compared therewith exceeding a selected threshold.

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