Patent ID: 8468898

Claim:
A method for encoding a shaft, comprising: (a) supplying current to a first location on the shaft through a first electrode and withdrawing current from a second location on the shaft through a second electrode, the current flowing through the shaft between the first and second electrodes forming first and second polarity magnetically polarized zones at the respective first and the second locations, the first and second electrodes circumferentially spaced apart relative to the shaft; (b) supplying current to a third location on the shaft through a third electrode and withdrawing current from a fourth location on the shaft through a fourth electrode the current flowing through the shaft between the third and fourth electrodes forming first and second polarity magnetically polarized zones at the respective third and fourth locations, wherein the third and fourth electrodes are circumferentially spaced apart relative to the shaft, wherein the step of supplying current to the first location is executed concurrently with the step of supplying current to the third location; (c) wherein the first electrode is axially spaced apart from the fourth electrode and the second electrode is axially spaced apart from the third electrode; (d) moving the first, second, third and fourth electrodes in unison along the shaft for forming additional magnetically polarized zones, wherein first and second magnetically encoded regions are formed on the shaft by merging of respective and adjacent first and second magnetically polarized zones, wherein third and fourth magnetically encoded regions are formed on the shaft by merging of respective and adjacent first and second magnetically polarized zones; and (e) when the first, second, third and fourth magnetically encoded regions reach a desired length, relocating the first, second, third and fourth electrodes on the shaft and repeating steps (a), (b), (c), and (d) until a plurality of the first, second, third and fourth magnetically encoded regions are formed on the shaft.