Passive solid-state magnetic field sensors and applications therefor
First Claim
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1. A system for detecting rate of flow of a fluid, the system comprising:
- a sensor having at least one multilayer material located adjacent to, but separated from, a circumference of a rotor wheel of a 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 detectable non-zero voltage signal in, the piezoelectric material, where at least a portion of the rotor wheel is in a flow path of, and is turned by flow of, a fluid, and where the rotor comprises one or more selected magnetic materials located at N locations (N≧
1) on the rotor circumference, and the N locations are approximately equally spaced along the circumference;
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; and
conversion means for receiving and converting the voltage sensing count to a value that is a measure of fluid flow rate of the fluid.
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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.
66 Citations
12 Claims
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1. A system for detecting rate of flow of a fluid, the system comprising:
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a sensor having at least one multilayer material located adjacent to, but separated from, a circumference of a rotor wheel of a 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 detectable non-zero voltage signal in, the piezoelectric material, where at least a portion of the rotor wheel is in a flow path of, and is turned by flow of, a fluid, and where the rotor comprises one or more selected magnetic materials located at N locations (N≧
1) on the rotor circumference, and the N locations are approximately equally spaced along the circumference;
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; and
conversion means for receiving and converting the voltage sensing count to a value that is a measure of fluid flow rate of the fluid. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for detecting fluid flow, the method comprising:
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locating a rotor so that at least a portion of the rotor wheel is in a flow path of, and is turned by flow of, a fluid;
providing a sensor with at least one multilayer material located adjacent to a circumference of a rotor wheel for the rotor, 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, where the rotor comprises one or more selected magnetic materials located at N locations (N≧
1) on the rotor circumference, and the N locations are approximately equally spaced along the circumference;
providing a voltage sensing means, connected to the piezoelectric material, 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; and
converting the voltage sensing count to a value that is a measure of flow rate of the fluid.
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Specification