Autonics BJ15M-TDT Photoelectric Sensor, Through Beam, 15m

The BJ15M-TDT: 15 m through-beam detection means the emitter and receiver are separate—you mount them facing each other across the gap, and anything that blocks the infrared beam triggers the output. That 15 m is the maximum clear-air range; real-world reach drops with dust, steam, or misalignment, so leave yourself a 20-30% margin if the environment is dirty. The NPN open-collector output sinks current to ground when the beam is broken (or made, depending on the Light ON / Dark ON switch). It's a standard three-wire DC sensor—brown to +VDC, blue to 0 V, black to the load. Selectable Light ON / Dark ON means you flip a switch on the sensor body to choose whether the output turns on when the beam is clear or when it's blocked; that saves you from having to invert the logic in the PLC.