The Siemens 3RG7420-7AB00 is a SIMATIC PXO310 K21R diffuse sensor — an energetic photoelectric unit in a compact 31x20x12 mm housing. It operates on 10-30V DC, delivers a PNP light-on output at 150 mA, and senses up to 500 mm. The M8 3-pole connector mates with standard quick-disconnect cables, and the IP68 rating means it survives washdown environments. The included M18 optics mount gives you a standard thread for bracket or through-hole installation.
The 500 mm sensing range is the rated detection distance for a standard white target (90% reflectance) — derate for darker surfaces or dusty conditions. The 150 mA output sink is the maximum continuous load on the PNP transistor; driving a PLC input directly is fine, but a relay or solenoid coil needs a flyback diode. IP68 allows submersion beyond 1 meter, but the M8 connector must be properly torqued and the mating cable rated for the same ingress protection.