Electrostatographic reproduction apparatus with electrometer control and

Abstract

An electrometer probe is used in an electrophotographic apparatus as part of a process control system to measure charge on a photoconductive film belt. This measurement is used to control voltage level or other process parameter of the electrophotographic process. The probe is supported in an electrometer probe holder so that a sensor aperture of the probe is at a fixed distance from the film belt. In order to ensure proper operation of the electrometer probe, a method and an apparatus for independently calibrating the electrometer probe is provided. A curved plate is provided on the electrometer probe holder. The plate is mounted at the same spacing from the probe aperture as the film belt. This plate has a receptacle for the service person's test lead to attach. The other end of the test lead is attached to a test point for the toning station bias supply. The probe may be reoriented on the probe holder to position the probe aperture at the fixed distance to the plate. Using a service test program, different biases are applied to the plate, and the response of the electrometer is monitored. In this way, troubleshooting of electrometer related errors is easily done without the need to remove the electrometer probe to a special test apparatus.