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.