Abstract: In a screening machine with a three-dimensional screening motion, a screen carrier for at least one screen plate is provided. The screen carrier is movable relative to a housing from which it is supported by springs. The screen carrier is driven by an electromagnetic drive device. The amplitude of oscillation of the screen carrier should be accurately readable, on the one hand, and, on the other hand, made adjustable for comparative tests. For this purpose, between the housing and the screen carrier an inductive displacement pickup for determining the amplitude of oscillation of the screen carrier is provided. This pickup is connected to a control unit which represents the determined amplitude of oscillation on an optical display and/or controls the electromagnet drive device to obtain a predetermined amplitude of oscillation.