Variable permeability magnetic field sensor and method
First Claim
1. A magnetic field sensor, comprising:
- a shell made of a magnetic material defining an interior;
a first conductor within said interior;
a second conductor within said interior, nested within said first conductor;
said first and second conductors exhibiting a mutual inductance between each other;
a source of electrical energy, interconnected with said first and second conductors, to establish an alternating electric current through at least one of said first and second conductors, and thereby a magnetic field in said shell;
a monitor, interconnected with one of said first and second conductors, to monitor changes in current therethrough as said shell is brought into proximity with an external magnetic field, to sense a change in permeability of said magnetic material.
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Accused Products
Abstract
A magnetic field sensor relies on variations in permeability of magnetic material to detect an external field. An exemplary magnetic field sensor includes a magnetic material and two or more conductors, at least one of which is connected to an electrical energy source. Current flowing through at least one of the conductors establishes a magnetic field in die magnetic material at a magnitude at which there is a generally linear relationship between the magnetic field and the permeability of the material. An external field to be sensed influences the permeability of the material. Sensing variations in the permeability of the magnetic material allows the external magnetic field to be sensed. Preferably, the conductors are mutually coupled and exhibit a mutual inductance between each other so that detectable changes in the current distribution between the conductors caused by an external magnetic field may be detected while the net current flowing in the conductors remains sufficient to maintain a magnetic field of sufficient magnitude in the material.
21 Citations
14 Claims
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1. A magnetic field sensor, comprising:
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a shell made of a magnetic material defining an interior;
a first conductor within said interior;
a second conductor within said interior, nested within said first conductor;
said first and second conductors exhibiting a mutual inductance between each other;
a source of electrical energy, interconnected with said first and second conductors, to establish an alternating electric current through at least one of said first and second conductors, and thereby a magnetic field in said shell;
a monitor, interconnected with one of said first and second conductors, to monitor changes in current therethrough as said shell is brought into proximity with an external magnetic field, to sense a change in permeability of said magnetic material. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A magnetic field sensor, comprising
a magnetic material; -
two mutually-coupled conductors driven by a source of alternating electricity to generate a magnetic field in said magnetic material, and having a mutual inductance dependent on the permeability of said magnetic material so that a change in permeability of said magnetic material results in re-distribution of current through said conductors;
a meter for measuring current through at least one of said first and second conductors to sense a change in permeability of said magnetic material caused by an external magnetic field, and thereby said external magnetic field.
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9. A method of sensing an external magnetic field, comprising:
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inducing a magnetic field in a magnetic element by providing alternating current through first and second mutually-coupled electric conductors having a mutual inductance dependent on the permeability of said magnetic element measuring a change in distribution of current in said two conductors, resulting from said external magnetic field varying the permeability of said magnetic element.
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10. A method of sensing a low frequency external magnetic field comprising:
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exciting a magnetic element with a time varying magnetic field having a frequency and amplitude to drive the permeability of said magnetic element to a state, at which there is a linear relationship between the permeability of said magnetic element and the external magnetic field to be detected;
sensing said external magnetic field by measuring variation of magnetic flux in said magnetic element, resulting from said external magnetic field. - View Dependent Claims (11, 12, 13, 14)
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Specification