The Siemens 3RG7421-0AA35 is a SIMATIC PXO320 K21R retro-reflective photoelectric sensor with an integrated polarization filter, sized 31x20x12 mm. It operates on DC 10-30V, outputs PNP dark-on at 150 mA, and detects up to 3 m. The unit is sealed to IP68, uses M18 optics, and terminates in a 350 mm PVC cable with a Molex connector.
Mounts via the M18 threaded optics barrel; the 31x20x12 mm body fits tight panel cutouts. The 350 mm PVC cable with Molex connector simplifies pre-wired harness replacement. Verify the PNP dark-on logic matches the PLC input card — a NO/NC mismatch at the sensor output will require a logic inversion in the control program or a separate converter. The 150 mA output drives standard 24 VDC PLC inputs directly, but check the input card's sink current rating to avoid overloading the sensor's transistor.