Measuring device for local measurement of an electrical property of the content of a container, wherein at least three electrodes are disposed adjacently of each other in height direction and electrically insulated from each other, wherein each of the electrodes can be connected to an electrical measuring circuit for measuring, via one of the electrodes and one other electrode connected to an electrical earth, the electrical property of the content of the container in the vicinity of the electrodes, and wherein the electrical measuring circuit is adapted to generate at least one electric measuring signal representing the measured electrical property, and a control unit for connecting the one electrode to the electrical measuring circuit and connecting the other electrode to an electrical earth.