Abstract: A method and apparatus for an electrographic printer or copier provides a first layer of toner particles is deposited on a first toner receiving surface by a force field. The amount of toner actually applied is detected at at least one point in the first layer. The force field is modified according to changes in the actual amount of toner from the predetermined amount of toner.

Abstract: A printer or copier has a developer station for a toner image wherein a photoconductive drum is provided with a latent charge image that is developed by applying a toner/air mixture to a developer drum that in turn applies the toner to the photoconductive drum. The toner is charged by a charging device as it is applied to the developer drum. A sensor senses the toner on the developer drum and a control varies the quantity of toner applied. The sensor is an optical sensor or a capacitive sensor, and the charge applied to the toner by the charging device is varied depending on the sensor output. A voltage applied to the developer drum may also be varied.

Abstract: A developer unit for an electrographic printer or copier has a toner receiving surface designed to receive a coating of toner particles. A toner mass sensor and a toner charge sensor measure a coting of toner particles on the toner receiving surface and send signals to an evaluation unit which calculates a mass-referred toner charge.