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Method and apparatus for calibrating a vehicle compass system

  • US 5,390,122 A
  • Filed: 05/07/1993
  • Issued: 02/14/1995
  • Est. Priority Date: 05/07/1993
  • Status: Expired due to Fees
First Claim
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1. A vehicle compass system comprising magnetic sensing means including a magnetic sensing device having first and second sensing coils positioned within the vehicle and adapted for producing first and second output signals that vary in accordance with changes in the directional heading of the vehicle, a control circuit including a microcomputer for producing first and second compensation signals that are supplied to said first and second sensing coils, respectively, to compensate for the remnant magnetic fields associated with the vehicle and for processing said first and second output signals from said magnetic sensing means and determining therefrom the heading direction of the vehicle and producing display output signals that are supplied to a display means adapted to display the heading direction of the vehicle;

  • the improvement comprising;

    memory means for storing predetermined values corresponding to the desired values for said first and second output signals when the vehicle is positioned in a single predetermined location and orientation;

    initiation means for initiating an initial calibration process when the vehicle is in said predetermined location and orientation; and

    wherein said microcomputer is programmed to be responsive to said initiation means for initially calibrating the compass system by reading said desired values from said memory means and generating appropriate compensation signals for both said first and second sensing coils to cause the actual output signals from said magnetic sensing means to bear a determined relationship to said desired values, and storing the values of said appropriate compensation signals.

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