An electrophotographic printing machine of the type having a latent image recorded
on an imaging member wherein said latent image is developed and transferred to
a media substrate during successive printing cycles of successive print jobs, including
a charging device for producing a voltage potential on the media substrate to transfer
the developed latent image to the media substrate, said charging device including
a coronode member and shield; a first voltage supply for apply a shield voltage
to said shield; a second voltage supply for applying a wire voltage to said coronode
member; a voltage monitor for measuring the voltage on the shield, said voltage
monitor periodically polling the voltage during a cycle of a print job and generating
a voltage measured signal as a function thereof; controller, responsive to a media
type of each media substrate and said voltage monitor, for adjusting said wire
voltage to said coronode member in respect to said shield voltage to said shield
to compensate for process impedance as said media substrate passes under said charging
device to obtained desirable image transfer.
