Double-sheet control sensors enable the reliable differentiation between one or more layers of very thin objects made of different materials. This allows, for example, single-layer paper sheets to be reliably pulled in or individual electrodes to be stacked for the production of a battery cell. Different operating principles, based on ultrasonics and capacitive sensors, cover the range of materials for different applications. Sensors for splice inspection detect desired and random splices in paper webs independent of the surface color and material properties.