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Prealigner probe

  • US 4,958,129 A
  • Filed: 03/07/1989
  • Issued: 09/18/1990
  • Est. Priority Date: 03/07/1989
  • Status: Expired due to Term
First Claim
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1. A system for capacitive edge detection of a supported member comprising:

  • a member where the position of an edge of said member is to be detected;

    a first probe positioned proximate to said member near the edge thereof and having a parameter varying as a function both of a distance from said probe to said member and displacement of a portion of said probe beyond the edge of said member;

    a second probe positioned near said first probe and closer to an interior location of said member than said first probe, said second probe having a parameter varying with distance of said second probe from said member;

    a first operational amplifier having the capacitance sensed by the electrode of the first probe in a feedback loop thereof;

    a second operational amplifier having the capacitance sensed by the electrode of the second probe in an input circuit thereof and;

    a source of A.C. excitation driving said first operational amplifier.

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