System and method for detecting the axial position of a shaft or a member attached thereto

A system of detecting a position of a movable member associated with a Cylinder, the system comprising:

• a shaft having a core, a first hardened metallic region from a surface of the shaft to a first radial depth from the surface at a first longitudinal position, and a second hardened metallic region from the surface of the shaft to a second radial depth at a second longitudinal position, the second radial depth different from the first radial depth, the hardened metallic regions overlying the core and formed from at least one of case hardening and inductive hardening of a metal or an alloy of the shaft;
• a sensor for sensing an eddy current or induced electromagnetic field to detect an alignment of at least one of the first hardened metallic region and the second hardened metallic region with reference to a fixed sensing region at a respective time;
• and
• a data processor for determining a longitudinal position of the shaft with respect to a cylinder at the respective time based on the sensed eddy current.