Abstract: The invention relates to a sensor for determining the structure-borne sound vibrations generated by the impingement of grains on a pulse detector in an agricultural machine for harvesting crops and to a device for operational monitoring of the sensor and improved signal evaluation.Such sensors are used to monitor threshing and separating performance at various points in a harvesting machine. Depending on the area of application, various forms of a pulse detector are used. These can have the shape of a plate, a tube, a rod or other similar profiles. Attached to these detectors are vibration detectors. A particularly strong connection between the vibration detector and the pulse detector is achieved by using a piezo-ceramic vibration sensor and its attachment by means of a screw connection.