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Method of and apparatus for detecting the rotation rate of an air moving fan

  • US 5,596,271 A
  • Filed: 05/03/1994
  • Issued: 01/21/1997
  • Est. Priority Date: 05/03/1994
  • Status: Expired due to Fees
First Claim
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1. A rotation rate sensor comprising:

  • a member rotatable about an axis;

    an interrupter fixed to the rotatable member so as to rotate therewith and define a circular path of travel upon rotation of the member;

    a Hall-effect device fixedly mounted relative to and adjacent the circular path of travel of said interrupter, said Hall-effect device having a given electrical output under ambient magnetic field conditions;

    a magnet having a magnetic field and being fixedly mounted in circumferentially spaced apart relation from the Hall-effect device about the axis and adjacent the circular path of travel of the interrupter such that the magnetic field of the magnet is insufficiently magnetically coupled to said Hall-effect device to cause any substantial change in the given electrical output of said Hall-effect device; and

    wherein said interrupter couples the magnetic field of said magnet to the Hall-effect device as it rotates on its path of travel past said magnet and Hall-effect device and causes a detectable difference in the electrical output of said Hall-effect device from the given electrical output thereof.

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