Compensation system for electronic compass

  • US 6,427,349 B1
  • Filed: 01/11/2001
  • Issued: 08/06/2002
  • Est. Priority Date: 12/20/1991
  • Status: Expired due to Fees
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First Claim
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1. A compensated electronic compass system suitable for use in a vehicle comprising:

  • an inside rearview mirror assembly, said assembly including a mirror mounting bracket for mounting said assembly in the vehicle;

    a two-axis compass sensor comprising a first magnetoresistive sensor and a second magnetoresistive sensor for detecting an external magnetic field and developing electronic signals representative of the strength and direction of said magnetic field, said external magnetic field being a combination of the earth magnetic field and a deviating magnetic field of the vehicle;

    each of said first and second sensors comprising at least one magnetoresistive field sensing element having a magnetic field sensitive axis and having an output which provides an output signal representative of a component of said external magnetic field along said sensitive axis, said first and second sensors being orientated with their sensitive axes in a predetermined angular relation with each other;

    a digital electronic circuit including a microcomputer coupled with said output of said first sensor and said output of said second sensor;

    said compass system providing a direction indicating signal to a compass heading display located within the vehicle, said direction indicating signal compensated for the deviating magnetic field of the vehicle so as to be representative of the magnetic heading of the vehicle;

    said compass system having an initial calibration mode to determine an initial deviation compensation for a particular vehicle installation and a normal calibration mode which is operative during normal compass operation;

    said compass system automatically exiting said initial calibration mode into said normal calibration mode after said initial deviation compensation is complete;

    wherein said two-axis compass sensor and said digital electronic circuit are located in a module that is secured to said mounting bracket of said inside rearview mirror assembly, wherein said compass heading display is mounted to said inside rear view mirror assembly and wherein said module communicates with said display, and wherein said magnetic field sensitive axis of said first magnetoresistive sensor is orientated orthogonal to said magnetic field sensitive axis of said second magnetoresistive sensor and wherein said magnetic field sensitive axis of said first magnetoresistive sensor is orientated parallel to the longitudinal axis of the vehicle when said two-axis compass sensor is mounted in the vehicle.

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