The Siemens 3RG7420-7GB00 is a SIMATIC PXO310 K21R diffuse photoelectric sensor in a compact 31x20x12 mm housing. It operates on DC 10-30V, with a 500 mm sensing range, NPN output configured light-on, and a 150 mA switching capacity. The M8 3-pole connector provides a quick-disconnect interface, and the IP68 rating allows submersion in washdown environments. The M18 optics thread means it mates with standard M18 mounting brackets or through-hole mounts.
The 500 mm range is the maximum detection distance for a standard white test card under the specified conditions; actual range on dark or matte targets will be shorter. The NPN light-on logic means the output transistor switches to ground when the received light exceeds the threshold — common for sinking inputs on PLCs. The 150 mA continuous current is the maximum load the sensor can drive directly; for higher loads, a relay or interface module is needed. The IP68 rating covers continuous immersion beyond 1 meter depth, but the M8 connector must be properly mated and the cable gland sealed to maintain that protection.