The Siemens 3RG7400-7GA00 is a SIMATIC PXO310 K21 diffuse sensor — an energetic photoelectric unit in a compact 31x20x12 mm housing. It operates on DC 10-30 V, outputs NPN dark-on at 150 mA, and connects via an M8 3-pole connector. The 50 cm sensing range suits close-proximity presence detection in conveyors or packaging lines, and the IP68 rating means it survives washdown environments without a secondary enclosure.
The 50 cm diffuse range is the headline figure — it defines the maximum reliable detection distance for a standard white card target. In practice, darker materials or dusty lenses reduce that reach; derate by 30-50% for black targets. The NPN dark-on output means the load is energized when the sensor sees the target (light blocked), which is the common fail-safe configuration for conveyor jam detection. The 150 mA sink current covers most PLC inputs and small relays directly, but check the load draw before paralleling multiple indicators. The M8 3-pole connector is a standard micro-style; verify your cable assembly matches the pin assignment (typically brown = V+, blue = GND, black = output).
Integration Notes
The 31x20x12 mm housing fits a standard 20 mm slot in sensor-mounting brackets. The M8 connector requires a mating cordset with a 3-pole female straight or right-angle connector — no field-wiring access inside the sensor body. Mounting orientation is flexible, but the sensing face must remain unobstructed; the IP68 seal is maintained only with the connector fully tightened and the O-ring in place. For washdown zones, orient the connector downward to prevent water pooling at the seal.