Measurement of electric charges on flowing toner with an electrostatic voltmeter

In every electrophotographic development system, the optimal charging and mass transfer processes are crucial for achieving high quality prints. Therefore, precise measurements of both charge and mass of toner become very important. This paper presents a novel method for measurements of the electric charge of the flowing electrophotographic toner particles. An electrostatic voltmeter (ESVM) is used for precise measurements of the voltage induced by charges carried by the flux of solid toner particles and by the charges generated on the walls of a dielectric pipe, while the toner is pneumatically transported through the pipe. Additionally, the total charge and mass of the toner are measured before and after passing through the pipe. In this way, voltages registered by the ESVM can be correlated with the amount of charge created by tribocharging. This allows for determination of tribocharging properties of the toner at a given particle flow velocity and for a given dielectric pipe material. The ESVM is a convenient, noncontacting, continuous, real-time charge monitoring tool.