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Method and apparatus for preventing contamination from affecting magnetic field sensors

  • US 9,157,970 B2
  • Filed: 04/05/2011
  • Issued: 10/13/2015
  • Est. Priority Date: 04/05/2011
  • Status: Active Grant
First Claim
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1. A power transmission unit comprising:

  • a rotatable element for transmitting power through the power transmission unit;

    a magnet for creating a magnetic flux that develops frequency variations proportional to a rotational velocity of the rotatable element; and

    a magnetic field sensor configured to sense the frequency variations and including;

    a sensor face provided with obstacles, wherein the obstacles constitute a series of grooves formed in the sensor face for preventing movement of contamination across the sensor face, anda sensor element located between the magnet and the sensor face,wherein contamination is caused to move in a first direction across the sensor face during rotation of the rotatable element, said obstacles being arranged in a second direction that is different from the first direction to inhibit movement of contamination across the sensor face so as to minimize false frequency variations in the magnetic flux.

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