Original Publication Date: 1989-Dec-31
Included in the Prior Art Database: 2004-Apr-05
Xerox Disclosure Journal
Increasing copy quality standards in electrophotographic printing machines places stricter requirements on process latitudes which, in turn, leads to an expansion of developability or process controls. One of the process variables important for process control is monitoring toner and developer material flow in actual development configurations. A calibrated, non-flow perturbing probe is located in the region of the material flow being measured. The probe monitors the noise generated by the charge density fluctuations. The noise detected by the probe is due to variations in the capacitive coupling of individual particles with the probe Both the power and noise spectrum are functions of the flow velocity. Depending upon the particular application, RMS voltage of the entire spectrum or power of specific bands of the spectrum is monitored and used either in a simple feedback loop or as only one process variable in a more complex control system.