Apparatus and method for sensing an angle of relative rotation of rotors

A relative rotation measurement apparatus comprising:

• a first rotor formed of at least an insulating magnetic material;
• a stationary core having a core body and an excitation coil, carrying an AC current, that in conjunction with the first rotor creates a magnetic circuit;
• a second rotor positioned between the first rotor and the stationary core
• oscillating means connected to the excitation coil for generating an oscillation signal;
• phase shifting means for shifting a phase of the oscillation signal in accordance with a magnitude of an eddy current generated at the second rotor;
• phase shift detecting means for detecting a phase shift of the oscillation signal;
• and
• measuring means for measuring an angle of relative rotation between the first rotor and the second rotor based on the detected phase shift.

A method comprising:

• attaching a first rotor formed of at least an insulating magnetic material to a first position of a shaft;
• providing a stationary body having an excitation coil, carrying an AC current, that in conjunction with the first rotor creates a magnetic circuit;
• attaching a second rotor to a second position of the shaft;
• and
• positioning the second rotor between the first rotor and the stationary body.

A method of measuring relative rotation, comprising:

• attaching a first rotor formed of at least an insulating magnetic material to a first shaft;
• providing a stationary body having an excitation coil, carrying an AC current, that in conjunction with the first rotor creates a magnetic circuit;
• attaching a second rotor to a second shaft;
• positioning the second rotor between the first rotor and the stationary body;
• generating an oscillation signal;
• shifting a phase of the oscillation signal in accordance with a magnitude of an eddy current generated at the second rotor;
• detecting a phase shift of the oscillation signal;
• and
• measuring, based on the detected phase shift, an angle of relative rotation between the first rotor and the second rotor.