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Helix current sense system

  • US 4,742,294 A
  • Filed: 07/16/1986
  • Issued: 05/03/1988
  • Est. Priority Date: 07/16/1986
  • Status: Expired due to Term
First Claim
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1. A current sensor, comprising:

  • (a) a magnetic sensing device comprising magnetic material;

    (b) current-carrying means associated with said sensing device;

    said magnetic material of said device having a predetermined permeability curve such that its permeability varies in relation to the temperature of said device and in relation to current that flows in said current-carrying means, said current-carrying means receiving a current to be measured;

    (c) means for applying a bias current to said current-carrying means and for adjusting said bias current according to ambient temperature so as to substantially avoid any variation in the permeability of said magnetic material due to changes in temperature;

    said bias current applying means including(1) a magnetic reference device comprising magnetic material;

    (2) current-carrying means associated with said reference device;

    said magnetic material of said reference device having a permeability curve substantially the same as that of said magnetic sensing device, such that its permeability varies in relation to the temperature of said reference device, and in relation to current that flows through said current-carrying means, in substantially the same way as in said magnetic sensing device;

    (3) means for providing a substantially constant reference current to said current-carrying means of said reference device;

    (4) means for measuring the permeability of said magnetic material of said magnetic reference device and for producing a feedback electrical output which is representative thereof;

    (5) a bias current generator for sensing the value of said feedback electrical output and for producing said bias current, said bias current being supplied to said current-carrying means of said magnetic reference device so as to maintain said feedback electrical output at a substantially constant level; and

    (6) means for conducting said bias current from said magnetic reference device to said current-carrying means of said magnetic sensing device; and

    (d) means for sensing the permeability of said magnetic material of said magnetic sensing device and producing an electrical output which is represenative of said pemeability and of said current to be measured.

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