Magnetic field sensor and method for sensing relative location of the magnetic field sensor and a target object along a movement line
AssigneeAllegro MicroSystems, LLC
InventorsThomas Kerdraon, Andreas P. Friedrich, Yannick Vuillermet
Life of this patent
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Abstract
A magnetic field sensor with a magnet is disposed proximate to a ferromagnetic target object having at least one ferromagnetic surface. The magnetic field sensor is operable to sense a relative location between the magnetic field sensor and the ferromagnetic target object along a movement line. In some embodiments, the target object is also spinning about a rotation axis parallel to the movement line. A corresponding method is described.
Claims58
A magnetic field sensor, comprising:
- a magnet operable to generate a DC magnetic field;
- and
- first and second magnetic field sensing elements operable to sense first and second influenced magnetic fields, respectively, related to the DC magnetic field but influenced by at least one ferromagnetic surface upon a ferromagnetic target object, wherein the first and second magnetic field sensing elements are disposed proximate to the at least one ferromagnetic surface, wherein the first and second magnetic field sensing elements are also operable to generate corresponding first and second electronic signals related to the first and second influenced magnetic fields, respectively, wherein a difference of amplitudes of the first and second electronic signals is related to a relative location of the magnetic field sensor and the ferromagnetic target object along a movement axis, wherein a change of the relative location is indicative of a relative displacement of the magnetic field sensor and the ferromagnetic object, and wherein the difference of the amplitudes of the first and second electronic signals is not related to a rotation of the ferromagnetic target object about a rotation axis passing through the ferromagnetic target object.
A method of sensing a relative location of a magnetic field sensor and a ferromagnetic target object along a movement axis, comprising:
- generating a DC magnetic field;
- placing a first magnetic field sensing elements proximate to at least one ferromagnetic surface of the ferromagnetic target object;
- placing a second magnetic field sensing elements proximate to the at least one ferromagnetic surface of the ferromagnetic target object;
- sensing, with the first and second magnetic field sensing elements, first and second influenced magnetic fields, respectively, related to the DC magnetic field but influenced by the at least one ferromagnetic surface;
- and
- generating, with the first and second magnetic field sensing elements, corresponding first and second electronic signals related to the first and second influenced magnetic fields, respectively, wherein a difference of amplitudes of the first and second electronic signals is related to the relative location of the magnetic field sensor and the ferromagnetic target object along the movement axis, wherein a change of the relative location is indicative of a relative displacement of the magnetic field sensor and the ferromagnetic object, and wherein the difference of the amplitudes of the first and second electronic signals is not related to a rotation of the ferromagnetic target object about a rotation axis passing through the ferromagnetic target object.
Dependencies are inferred from the claim text.