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Inductive displacement sensors

  • US 4,991,301 A
  • Filed: 02/10/1989
  • Issued: 02/12/1991
  • Est. Priority Date: 02/27/1987
  • Status: Expired due to Term
First Claim
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1. Apparatus for use in monitoring displacement along a displacement path, said apparatus comprising first and second members extending along said displacement path and separated by a constant spacing, said first member comprising a wound portion having a single winding which provides a multiplicity of serially connected coil portions arranged as wound salient poles disposed successively along said displacement path with the axes thereof intersecting said displacement path;

  • said poles being wound so that alternate poles are of opposite polarity;

    said multiplicity of serially connected salient poles including a first terminal at one end of the series of poles, a second terminal at the other end of the series of poles, and a central tapping connection;

    said second member comprising an inductance varying means for providing, along with displacement path, regions of different effective permeability to alternating magnetic flux which affect the inductances of adjacent coil portions of said single winding;

    at least a portion of said inductance varying means being displaceable relative to said first member along said displacement path to effect displacement of the regions of different effective permeability relative to said coil portions of said single winding such that, for any relative position, the coil portions of one half of the length of the wound portion have higher inductance than the coil portions of the other half;

    the apparatus further including means for supplying an alternating electrical voltage across said first and second terminals so that, when alternating current is applied across said terminals and said relative displacement is effected, the voltage at the central tapping connection varies with a substantially linear analog characteristic for a displacement corresponding to one half of the length of the wound portion, and continued displacement in the same sense for a further half length restores the voltage to its original value in a symmetrical manner;

    said voltage providing analog electrical output data relating to said displacement.

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