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Rotational velocity and direction sensing system

  • US 6,498,474 B1
  • Filed: 06/27/2001
  • Issued: 12/24/2002
  • Est. Priority Date: 06/27/2001
  • Status: Expired due to Term
First Claim
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1. A rotational sensor system for detecting rotational velocity and rotational direction of a rotatable member rotatable in a forward and in a reverse rotational direction about an axis of rotation, the rotational sensor system comprising:

  • a rotatable element adapted to operatively engage and rotate with the rotatable member about the axis of rotation, with the rotatable element having a generally circular periphery that includes means, spaced about the periphery, for creating magnetic field variations;

    first sensor means, adjacent to the periphery, for sensing variations in a magnetic field and producing an electric signal in response thereto;

    second sensor means, adjacent to the periphery and circumferentially spaced about the periphery from said first sensor means, for sensing variations in a magnetic field and producing an electric signal in response thereto;

    means for generating a magnetic field;

    means for receiving the electric signals from the first sensor means and second sensor means and detecting a phase shift between the signals from the first sensor means and the second sensor means; and

    means for generating an output signal including a series of square waves having frequencies corresponding to the rotational velocity of the rotatable element and having amplitudes that are in a first range when the rotatable element is rotating in the forward direction and in a second range when the rotatable element is rotating in the reverse direction, and including a dead amplitude zone between the first range and the second range of amplitudes for the square waves.

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