Abstract: A shaft comprises a hardened outer metallic layer having a first hardness level with a generally uniform radial depth. A first strip extends in a generally longitudinal direction in the outer metallic layer. The first strip has a second hardness level different from the first hardness level. A second strip in the outer metallic layer has the second hardness level. The first strip and the second strip are spaced apart from each other over at least a longitudinal region. A sensor senses an angular difference between a first magnetic field associated with the first strip and a second magnetic field associated with the second strip. A data processor references an established relationship between a position of the shaft and the angular difference between magnetic fields associated with the first strip and the second strip to detect a Position of the shaft with respect to a reference point.

Abstract: An improved proximity sensing circuit and method is provided. In particular, the proximity sensing system includes an improved controller comprising a programmable logic device (“PLD”). In one particular aspect of the invention, the controller includes a field programmable gate array (“FPGA”) controller. In general, the proximity sensing system measures the AC and DC resistances of a proximity sensor and a precision resistor and, from these measured values, calculates a compensated resistance. The compensated resistance may be used to determine the gap. The measured AC and DC resistances of the proximity sensor may be used to perform a self diagnostic on the sensing system and aid in determining a system fault.