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Hall effect sensing apparatus and method

  • US 4,829,248 A
  • Filed: 09/20/1984
  • Issued: 05/09/1989
  • Est. Priority Date: 09/20/1984
  • Status: Expired due to Term
First Claim
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1. An encoder for providing an electrical output indicative of the annular behavior of a magnetized wheel comprising:

  • a unitary supporting frame having two spaced locating portions;

    a magnetized wheel supported for rotation at one of said locating portions, said wheel having a magnetized periphery of alternating north and south poles;

    a magnetic field-responsive sensor fixedly supported on said frame at the other of said locating portions proximate the wheel periphery to be influenced by wheel motion and the correlative changes in the magnetic field incident on the sensor, said sensor directly engaging said other locating portion thereby to be located relative to said wheel with substantially the same degree of accuracy as the spacing on said frame between said two locating portions; and

    a calibrating permanent magnet supported on the frame closely adjacent to the sensor and mechanically movable relative to said sensor to an adjusted fixed position, the calibrating magnet field after the aforesaid adjustment being constant and also being incident on the sensor such that the sensor is responsive to the resultant of the fields of the adjustably fixed calibrating magnet and the magnetized wheel, said calibrating permanent magnet being of generally cylindrical shape magnetized in a direction generally orthogonal to the cylinder axis to provide diametrically opposite north and south poles, adjustment being made by rotation of the cylinder about its axis to apply the field of a selected one of said north and south poles to said sensor.

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