Passive solid-state magnetic field sensors and applications therefor
First Claim
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1. A system for detecting rotational speed of a rotor, the system comprising:
- a sensor comprising at least one multilayer material located adjacent to, but separate from, a rotatable rotor, the multilayer material comprising a layer of a first selected thickness of a selected magnetostrictive material, connected across an interface to a layer of a second selected thickness of a selected piezoelectric material and configured so that, when the magnetostrictive material is subjected to a change in magnetic field from rotation of the rotor, a change in at least one dimension of the magnetostrictive material induces a strain in, and produces a non-zero voltage signal in, the piezoelectric material, where the rotor comprises one or more selected magnetic materials located at N locations (N≧
1) on a circumference of the rotor, and the N locations are approximately equally spaced along the circumference; and
voltage sensing means connected to the piezoelectric material layer to sense and count a number of times the voltage signal attains or exceeds a selected value in a selected time interval as the rotor wheel rotates.
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Abstract
Passive solid-state magnetic sensors are based on the combination of magnetorestrictive materials and piezoelectric materials. Sensors have applications in rotor speed detection, magnetic field detection, read heads, and MRAM, for example.
23 Citations
14 Claims
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1. A system for detecting rotational speed of a rotor, the system comprising:
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a sensor comprising at least one multilayer material located adjacent to, but separate from, a rotatable rotor, the multilayer material comprising a layer of a first selected thickness of a selected magnetostrictive material, connected across an interface to a layer of a second selected thickness of a selected piezoelectric material and configured so that, when the magnetostrictive material is subjected to a change in magnetic field from rotation of the rotor, a change in at least one dimension of the magnetostrictive material induces a strain in, and produces a non-zero voltage signal in, the piezoelectric material, where the rotor comprises one or more selected magnetic materials located at N locations (N≧
1) on a circumference of the rotor, and the N locations are approximately equally spaced along the circumference; and
voltage sensing means connected to the piezoelectric material layer to sense and count a number of times the voltage signal attains or exceeds a selected value in a selected time interval as the rotor wheel rotates. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for detecting rate of rotation of a wheel, the method comprising:
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providing a sensor with at least one multilayer material located adjacent to a circumference of a rotor wheel for a rotor, the multilayer material comprising a layer of a first selected thickness of a selected magnetostrictive material located contiguous to a layer of a second selected thickness of a selected piezoelectric material and configured so that, when the magnetostrictive material is subjected to a change in magnetic field, a change in at least one dimension of the magnetostrictive material induces a strain in, and produces a non-zero voltage signal in, the piezoelectric material, where the rotor comprises one or more selected magnetic materials located at N locations (N≧
1) on a circumference of the rotor, and the N locations are approximately equally spaced along the circumference; and
providing a voltage sensing means, connected to the piezoelectric material layer, to sense and count a number of times the voltage signal attains or exceeds a selected value in a selected time interval as the rotor wheel rotates.
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11. A system for detecting electrical current, the system comprising:
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an electrical conductor that can support an electrical current;
at least one multilayer material, positioned adjacent to the conductor, the multilayer material comprising a layer of selected thickness of a selected magnetostrictive material located contiguous to a layer of selected thickness of a selected piezoelectric material and configured so that, when the magnetostrictive material is subjected to a change in magnetic field, a change in at least one dimension of the magnetostrictive material induces a strain in, and produces a non-zero voltage signal in, the piezoelectric material;
a source of a bias magnetic field having a selected magnetic field strength in a region surrounding the multilayer material;
a voltage sensing means, connected to the piezoelectric material layer, to determine a selected function value for the voltage in a selected time interval as electric charge flows in the conductor and to convert the voltage function value to a current value that is a measure of electrical current during the selected time interval. - View Dependent Claims (12)
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13. A method for detecting electrical current, the method comprising:
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providing an electrical conductor that can support an electric current;
positioning at least one multilayer material adjacent to the conductor, the multilayer material comprising a layer of selected thickness of a selected magnetostrictive material located contiguous to a layer of selected thickness of a selected piezoelectric material and configured so that, when the magnetostrictive material is subjected to a change in magnetic field, a change in at least one dimension of the magnetostrictive material induces a strain in, and produces a non-zero voltage signal in, the piezoelectric material;
providing a bias magnetic field having a selected magnetic field strength in a region surrounding the multilayer material;
providing a voltage sensing means, connected to the piezoelectric material layer, to determine a selected function value for the voltage in a selected time interval as electrical charge flows in the conductor; and
converting the voltage function value to a current value that is a measure of electrical current in the conductor during the selected time interval. - View Dependent Claims (14)
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Specification