A method for measuring a property of a measuring coil, which is modeled as a parallel circuit including a capacitance with a series circuit including a DC voltage resistance, a frequency-dependent resistance, and an inductance, and a current-voltage converter is connected in series, by performing: applying an AC voltage, having a first frequency and having a DC voltage component differing from zero, to the coil and a voltage at the current-voltage converter is captured at a second frequency which is a multiple of the first frequency, wherein the multiple is an n-tuple, and the impedance and the phase angle at the first frequency are derived from at least n measured values captured in succession; and applying an AC voltage, having a third frequency differing from the first frequency and having a DC voltage component differing from zero, to the coil and the voltage at the current-voltage converter is captured at the second frequency or at a fourth frequency which is a multiple of the fourth frequency, wherein the multiple is an m-tuple, and the impedance and the phase angle at the third frequency are derived from m measured values captured in succession; at least one of the values for the DC voltage resistance, the frequency-dependent resistance, and the inductance being derived from the impedances and the phase angles.

A magnetic field sensor has a plurality of magnetic field sensing elements and operates as a motion detector for sensing a rotation or other movement of a target object.

A position sensing system for measuring a position of a linearly moving object includes a high magnetic permeability material positioned on the moving object, an electromagnet configured to generate an alternating magnetic field, and at least one magnetic sensor configured to measure an intensity of a first magnetic field that is based on the alternating magnetic field. A controller is configured to estimate a linear position of the moving object based on the measured intensity of the first magnetic field.

A system for detecting a position of a dual solenoid device includes device configured to move between first and second positions, and a controller. The controller has first and second monitoring circuits in operable communication with first and second channels, respectively. The first and second channels are in operable communication with first and second solenoids, respectively. Each solenoid is configured to selectively operate as an active solenoid to move the device when the solenoid and its respective channel are in an active mode, and as a passive solenoid when the solenoid and its respective channel are in a passive mode to passively move with the active solenoid. Each of the monitoring circuits is configured to determine a position of the device when the channel the monitoring circuit is associated with is operating in the passive mode by monitoring an electrical parameter of the passive solenoid associated with that channel.

Methods and apparatus for detecting a magnetic field include a semiconductor substrate, a coil configured to provide a changing magnetic field in response to a changing current in the coil; and a magnetic field sensing element supported by the substrate. The coil receives the changing current and, in response, generates a changing magnetic field. The magnetic field sensing element detects the presence of a magnetic target by detecting changes to the magnetic field caused by the target and comparing them to an expected value.

Methods and apparatus for detecting a magnetic field include a semiconductor substrate, a coil configured to provide a changing magnetic field in response to a changing current in the coil; and a magnetic field sensing element supported by the substrate. The coil receives the changing current and, in response, generates a changing magnetic field. The magnetic field sensing element detects the presence of a magnetic target by detecting changes to the magnetic field caused by the target and comparing them to an expected value.

An apparatus comprises a conductive material having varying thickness along its length, the varying thickness providing varying response along a length of the conductive material to a magnetic field having a non-zero frequency; wherein the magnetic field produces an eddy current in the conductive material which generates a reflected magnetic field, wherein the varying response causes the reflected magnetic field to vary in strength along the length of the conductive material. The apparatus may include one or more reference portions of conductive material.

A wheel speed sensor may comprise a magnet; an induction coil coupled to the magnet; a rotor comprising a plurality of teeth, wherein the magnet is disposed proximate the plurality of teeth; a gear system coupled to the rotor comprising an initial gear, wherein the initial gear may be configured to be coupled to a wheel and configured to rotate at a speed equal to a wheel rotational speed of the wheel. The gear system may be configured to cause a rotor rotational speed of the rotor to be greater than the wheel rotational speed in response to the wheel rotating.

The present disclosure describes a two-stage method for estimating an angle offset of an angle sensor in a system comprising a permanent-magnet synchronous motor. An initial value for the estimated angle offset is first determined with a short circuit test. Next, a torque of the motor may be controlled so that the motor is maintained at a zero speed. Minor adjustments are made to the value of the angle offset to find a minimum magnitude of stator current. A value at which the stator current is at its minimum is used as a final angle offset.

Methods and apparatus for detecting a magnetic field include a semiconductor substrate, a coil configured to provide a changing magnetic field in response to a changing current in the coil; and a magnetic field sensing element supported by the substrate. The coil receives the changing current and, in response, generates a changing magnetic field. The magnetic field sensing element detects the presence of a magnetic target by detecting changes to the magnetic field caused by the target and comparing them to an expected value.