Methods and apparatus for magnetic sensor having an integrated coil or magnet to detect a non-ferromagnetic target
First Claim
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1. A magnetic field sensor comprising:
- a substrate having first and second opposing surfaces;
a magnetic source configured to provide a magnetic field to induce an eddy current in a non-ferromagnetic rotating target having a body with an oblong, oval shape affecting the eddy current, wherein the magnetic source is a coil positioned so that the substrate is between the magnetic source and the target;
a magnetic field sensing element configured to detect the magnetic field provided by the magnetic source and a resulting magnetic field generated as a result of the eddy current and produce a signal representing a combination of the magnetic field provided by the magnetic source and the resulting magnetic field generated as a result of the eddy current; and
a circuit formed within the substrate and coupled to receive the signal and determine a position of the rotating target,wherein the substrate is positioned so a plane defined by the first surface is substantially parallel to an axis of rotation of the rotating target; and
wherein a shortest distance between the magnetic field sensing element and the rotating target changes as a result of rotation of the oblong, oval shape of the body, and a strength of the eddy current and a strength of the resulting magnetic field changes in response to changes in the shortest distance between the magnetic field sensing element and the rotating target.
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Abstract
Methods and apparatus for detecting a magnetic field include a magnetic source configured to provide a magnetic field to induce an eddy current in a non-ferromagnetic target, and a magnetic field sensing element configured to detect the magnetic field as a result of the eddy current. The magnetic field provided by the magnetic source can be a static (i.e. DC) field or a changing (i.e. non-DC) field.
415 Citations
16 Claims
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1. A magnetic field sensor comprising:
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a substrate having first and second opposing surfaces; a magnetic source configured to provide a magnetic field to induce an eddy current in a non-ferromagnetic rotating target having a body with an oblong, oval shape affecting the eddy current, wherein the magnetic source is a coil positioned so that the substrate is between the magnetic source and the target; a magnetic field sensing element configured to detect the magnetic field provided by the magnetic source and a resulting magnetic field generated as a result of the eddy current and produce a signal representing a combination of the magnetic field provided by the magnetic source and the resulting magnetic field generated as a result of the eddy current; and a circuit formed within the substrate and coupled to receive the signal and determine a position of the rotating target, wherein the substrate is positioned so a plane defined by the first surface is substantially parallel to an axis of rotation of the rotating target; and wherein a shortest distance between the magnetic field sensing element and the rotating target changes as a result of rotation of the oblong, oval shape of the body, and a strength of the eddy current and a strength of the resulting magnetic field changes in response to changes in the shortest distance between the magnetic field sensing element and the rotating target. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of detecting a magnetic field comprising:
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placing a substrate, which has a surface that supports one or more magnetic field sensing elements, on a first surface of a lead frame; enclosing the substrate ad a coil in a non-conductive mold material, wherein the coil is adjacent to a second surface of the lead frame opposite the first surface of the lead frame; placing the enclosed substrate and coil in proximity to a non-ferromagnetic rotating target so that a plane defined by the surface is substantially parallel to an axis of rotation of the non-ferromagnetic rotating target; producing, by the coil, a magnetic field to induce an eddy current in the non-ferromagnetic rotating target; causing fluctuations in the eddy current by features of the non-ferromagnetic rotating target passing through the magnetic field; detecting, by the one or more magnetic field sensing elements, variations in a resulting magnetic field generated by the non-ferromagnetic rotating target; and determining, by a processor, a position of the rotating target based on the resulting magnetic field; wherein a shortest distance between the one or more magnetic field sensing elements and the target changes as a result of rotation of the target, and a strength of the eddy current and a strength of the resulting magnetic field detected by the one or more magnetic field sensing elements changes in response to changes in the shortest distance between the one or more magnetic field sensing elements and the target.
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15. A magnetic field sensor comprising:
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a lead frame having a first and second opposing surfaces; a coil adjacent to the second surface of the lead frame and configured to provide a changing magnetic field in response to being energized with a changing current to induce an eddy current in a non-ferromagnetic rotating target; a substrate having first and second opposing surfaces, the second surface of the substrate attached to the first surface of the lead frame and the first surface of the substrate supporting; a magnetic field sensing element configured to detect the changing magnetic field provided by the coil and a resulting magnetic field generated as a result of the eddy current and produce a signal representing a combination of the changing magnetic field provided by the coil and the resulting magnetic field generated as a result of the eddy current; and a circuit formed within the substrate and coupled to receive the signal and determine a position of the rotating target; wherein the first surface of the substrate defines a plane that is substantially parallel to an axis of rotation of the non-ferromagnetic rotating target; and wherein a shortest distance between the magnetic field sensing resin element and the target changes as a result of rotation of the target, and a strength of the eddy current and a strength of the resulting magnetic field detected by the magnetic field sensing element changes in response to changes in the shortest distance between the magnetic field sensing element and the target wherein the coil is positioned so that the substrate is between the coil and the target. - View Dependent Claims (16)
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Specification