Abstract: A roller conveyer transports sheet material to accumulating hoppers provided with rotatable distributing chutes. Chute drivers are electrically connected to a unit for measuring the material thickness via a control unit. The thickness measuring unit comprises a radioisotope thickness gauge including a radiation detector and a radioactive source, positioned on opposite sides of the sheet material between two pairs of drive rollers of the conveyer. A meter measures the average value of the radiation intensity during a period of time within which a single sample of the material being sorted passes through the radiation zone. Another meter measures the instantaneous value of the radiation intensity.

Abstract: An apparatus for contactless measurement of the thickness of a sheet material comprises a radioactive source located in a protective container which has a collimating hole to output a flow of radiation. There is a radiation detector to sense the radiation passed through the material under control, which is electrically connected to a radiation intensity meter, and also compressed air means for delivery of a jet of compressed air to the measurement point.