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Zero-offset magnetometer having coil and core sensor controlling period of an oscillator circuit

DC
  • US 5,239,264 A
  • Filed: 11/14/1991
  • Issued: 08/24/1993
  • Est. Priority Date: 11/14/1991
  • Status: Expired due to Term
First Claim
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1. A magnetometer for measuring an external magnetic field, comprising:

  • a relaxation oscillator circuit comprising;

    driver means having an input terminal and an output terminal for providing an oscillating signal at said output terminal;

    sensor means having a first coil wound on a first high magnetic permeability core for controlling the period of said oscillator circuit, said first coil having first and second first-coil terminals, and said first coil being electrically symmetric between said first and second first-coil terminals;

    a first first-coil resistor coupled to said first first-coil terminal;

    a second first-coil resistor coupled to said second first-coil terminal, said second first-coil resistor and said first first-coil resistor being impedance matched;

    switching means coupled to said first and second first-coil terminals and to said input terminal of said driver means for coupling said input terminal alternately to said first first-coil terminal and to said second first-coil terminal; and

    gate means coupled to said first first-coil resistor and to said second first-coil resistor for shunting said first first-coil resistor to a DC potential when said switching means couples said input terminal of said driver means to said second first-coil terminal, and for shunting said second first-coil resistor to said DC potential when said switching means couples said input terminal of said driver means to said first first-coil terminal;

    measurement means for analyzing the output signal from said output terminal of said driver means, and for providing a signal representing the magnitude of said external magnetic field strength.

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