WL250-2R1531 W250-2 Photoelectric Sensor Retroreflective 0.01 → 15 m. SICK W250-2 series photoelectric sensors have long adjustable sensing distances. Designed for use in a wide variety of applications that reach far beyond handling, packaging, warehousing and wood industries. A visible red light used for an alignment aid makes the W250 photoelectric sensors particularly user-friendly.