Abstract: A length separator comprising at least one rotational member, e.g. a disc or a cylinder, having cells for lifting seeds and other particles from a lower position to a higher position, and a trough for receiving the lifted material. The rotatable member is associated with at least one sensor located in the flow of the lifted material supplied to the trough, for generating an electric signal in dependence on impingement of material particles leaving the rotatable member and falling down into the trough. The sensor is operatively connected through an electronic function unit to adjusting means for controlling the flow of material to be cleaned which is supplied to the separator, in dependence on the impingement intensity.

Abstract: An arrangement in grading and cleaning machines with a screen (15). The screen is associated with at least one sensor (24) in the flow of material passing through the screen for generating electric signals in dependence on material particles leaving the screen as throughput and impinging on the sensor. The sensor is operatively connected to be adjusted (26) through a function circuit (25) for the control of various operations parameters of the screen (15) in dependence on the impingement intensity to achieve a throughput according to a predetermined mathematical model.

Abstract: An arrangement in machines for separating materials having different aerodynamic properties and employing an air current for actuating the materials.A sensor is located in the path of particles carried along by the air current, to generate electric signals in dependence on particles impinging the sensor. The sensor is operatively connected to a control for regulating the flow rate of the air current in order to obtain an air flow corresponding to a predetermined impingement intensity.