Magnetic field sensor with modulated diagnostic signal

A magnetic field sensor comprising:

• a coil configured to generate a magnetic field having a first frequency, wherein the magnetic field induces a reflected magnetic field from a target;
• means for generating a diagnostic magnetic field having a second frequency different than the first frequency, wherein the diagnostic magnetic field does not induce a reflected magnetic field from the target that is measurable by the magnetic field sensor;
• means for detecting the reflected magnetic field and the diagnostic magnetic field and generating a signal that simultaneously represents the reflected magnetic field and the diagnostic magnetic field;
• and
• means for extracting a portion of the signal representing the diagnostic magnetic field.

A magnetic field sensor comprising:

• a first coil configured to generate a magnetic field having a first frequency, wherein the magnetic field induces a reflected magnetic field from a target;
• a second coil configured to generate a diagnostic magnetic field having a second frequency, the second coil including a first lobe and a second lobe, the first and second lobes each including a first winding portion having a first winding direction and a second winding portion having a second winding direction that is opposite to the first winding direction;
• at least two magnetic field sensing elements to detect the reflected magnetic field and the diagnostic magnetic field and to generate a signal representing the reflected magnetic field and the diagnostic magnetic field, at least one of the magnetic field sensing elements being positioned between the first and second winding portions of the first lobe, and at least one of the magnetic field sensing elements being positioned between the first and second winding portions of the second lobe;
• and
• a processing circuit coupled to the at least two magnetic field sensing elements and configured to:
• receive the signal;
• extract a diagnostic magnetic field portion of the signal representing the diagnostic magnetic field;
• and generate an error signal if the diagnostic magnetic field portion of the signal represents a fault.

A magnetic field sensor comprising:

• a first coil configured to generate a magnetic field having a first frequency, wherein the magnetic field induces a reflected magnetic field from a target;
• a second coil configured to generate a diagnostic magnetic field having a second frequency, the second coil including a first lobe and a second lobe, the first and second lobes each including a first winding portion having a first winding direction and a second winding portion having a second winding direction that is opposite to the first winding direction;
• at least two magnetic field sensing elements to detect the reflected magnetic field and the diagnostic magnetic field and to generate a signal representing the reflected magnetic field and the diagnostic magnetic field;
• and
• a processing circuit coupled to the at least two magnetic field sensing elements and configured to:
• receive the signal;
• extract a diagnostic magnetic field portion of the signal representing the diagnostic magnetic field;
• and generate an error signal if the diagnostic magnetic field portion of the signal represents a fault,
• wherein the first and second winding portions produce canceling magnetic fields so that the second coil does not induce a reflected magnetic field from the target.