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Scaling system and method for an electronic compass

  • US 5,351,204 A
  • Filed: 12/27/1991
  • Issued: 09/27/1994
  • Est. Priority Date: 12/27/1991
  • Status: Expired due to Term
First Claim
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1. A scaling compensation method for use in a vehicle electronic compass control circuit that includes a microcomputer, a flux-gate having an output voltage dependent upon a strength of the earth'"'"'s magnetic field and a magnetic field of the vehicle incorporating the electronic compass control circuit and their direction, and an integrator having a fixed output voltage range and producing an output containing heading information;

  • the control circuit employing a scaling compensation circuit that includes a multi-bit analog-to-digital converter coupled between the output of said integrator and said microcomputer and a ranging circuit, said ranging circuit employing variable resistance negative feedback connected to the output of said integrator, said electronic compass adapted to determine vehicle heading as a function of the earth'"'"'s magnetic field wherein the earth'"'"'s magnetic field is distorted by the magnetic field of the vehicle, said scaling compensation method comprising;

    (a) monitoring said integrator output for 360°

    of vehicle headings;

    (b) partitioning said integrator output into a predetermined number of discrete ranges;

    (c) converting the discrete ranges into digital values;

    (d) counting the number of digital values and comparing the number to a predetermined number of digital values;

    (e) decreasing the resistance of said variable resistance negative feedback to a predetermined level and decreasing the number of discrete ranges if the digital value is less than or equal to the predetermined number of digital values; and

    (f) converting said digital values into digital vehicle heading information.

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