Method and apparatus for drum corona current measurement and alignment

Abstract

Method and apparatus for enabling measurement of corona drum current in an electrostatic copier as a maintenance aid. A rotatable drum supports a photoconductor with a conductive backing connected to a ground current return path including a slip ring. In the maintenance mode, the ground path is opened allowing drum current to flow through a current measuring circuit including a pair of jacks to which a measurement device may be connected. The current measuring circuit also develops a potential which is representative of whether or not the current return path is grounded. This potential is coupled to a monitoring device where it may be used to drive a display. A method of aligning a corona generator employing the corona current measuring apparatus of the invention is applicable for aligning corona generators in situ in an electrostatic copier. The alignment method includes steps of energizing a selected corona generator, interrupting the normal ground return path, providing a current path from the photoconductor and coupling the current path to a measurement device. For alignment purposes, at least two measurements are made, each measurement is made while different portions of the corona generator are masked. The measurements provide a measure of the corona current generated by two different portions of the generator which is useful in aligning the generator.