Magnetic encoder apparatus capable of resolving axial and rotational displacements

An encoder apparatus comprising:

• a housing including a cavity and an opening extending from the cavity to the top of the housing:
• a knob shaft including an upper portion disposed through the housing opening, and a lower portion disposed in the cavity and including a permanent magnet magnetized with at least one set of North-South magnetic poles, said knob shaft and its permanent magnet being rotatably movable in the housing cavity;
• a plurality of magnetic field sensors disposed within the housing cavity in proximity to said permanent magnet and distributed angularly thereabout, each sensor for sensing magnitude of the magnetic field strength of said permanent magnet, said sensed magnitude changing as the orientation of the permanent magnet changes rotationally with respect to said sensor, each sensor for generating an analog signal of an amplitude substantially proportional to the magnitude of the magnetic field strength sensed thereby;
• and
• a processor for processing said sensor signals to resolve rotational movement of the knob shaft and determine a rotational angle of the knob shaft as a function of the amplitudes of said sensor signals, said processor including means for computing a count based on a function of a determined change in rotational angle of the shaft and a predetermined incremental change in rotational angle.