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.

Abstract: An apparatus for fine grinding of, in particular, material samples for laboratory experiments. The apparatus has a fixed grinding member and a rotating grinding member, which are disposed in such a way that each has a surface facing the other and slightly spaced therefrom, with the material which is to be ground being received and passed between these surfaces. The problem faced by such an apparatus is that samples have to be introduced and discharged one by one, so that the work is carried out as a batch process. It is also difficult to accurately adjust the grinding degree. In order to solve these problems, and to carry out a continuous grinding of hard and very hard materials, as well as to be able to adjust the grain size of the grinding, the invention proposal is that the grinding members on the one hand be a fixed cylindrical body and on the other hand be a roller body which rotates coaxially therein.