The device has a vibration sensor such as micro-mechanical-electrical systems (MEMS) which is conductively connected to a vibration axis (58) of a conveyor roller (30) that is arranged relative to a rotatable drum (40). An evaluation device connected to vibration sensor, emits a warning signal if vibration sensor detects the penetration of foreign material into conveying roller. The sensitive frequency range of vibration sensor is above 4 kHz. An independent claim is included for harvesting machine.
