The 3RG40 38-3GD00: The Siemens 3RG4038-3GD00 is a 40 x 40 mm inductive proximity sensor with a 15 mm sensing distance, NPN output, and M12 4-pin connector. It switches up to 200 mA at 15–34 V DC, with a selectable normally-open or normally-closed output. The 15 mm range means it detects metal targets at a gap that suits part-present sensing on conveyor lines or end-stop detection on linear actuators — enough stand-off to avoid collision damage from passing workpieces.
The M12 connector and 40 x 40 mm body drop into standard sensor brackets. NPN output pulls the load to ground — common in older PLC input cards or sinking-logic circuits. The 15–34 V DC supply range covers 24 V nominal industrial busses with headroom for brownout conditions down to 15 V.