With the sensors, an infrared light-band illuminates a CCD line. A passing object can thereby be measured by its occlusion. The resolution of 14 µm and the high reproducibility enable the reliable measurement of very fine yarns and wires. The variety of implementable measurement functions enables the position detection of transparent edges, the determination of the thinnest or thickest wire and much more. The vacuum resistance of the devices also enables use in carbon fiber production.