Abstract: A charge detector forming part of a device for controlling the electrostatic charge applied to ink drops in an ink-jet printer comprises at least one internal conductive cylindrical rod connected to an electronic circuit and surrounded by an insulating sleeve. The sleeve is tightly fitted within an outer conductive cylinder which is connected to ground. A calibrated slot of predetermined length and width is formed so as to provide a passageway for the flow of ink drops through the detector. As each ink drop passes in front of the conductive cylindrical rod, a signal is induced and processed by the electronic circuit. The device also serves to control at least one ink-pressurizing pump with a view to ensuring constant flow velocity of the ink drops.