Retroreflective sensing at 1-20 cm
The Omron E3T-SR12 is a retroreflective photoelectric sensor with a sensing range of 1-20 cm, using an NPN output. This means it detects objects by sensing the light reflected back from a separate reflector, not the object itself. The 1-20 cm range suits it for short-distance presence detection on conveyors or in packaging machinery where the sensor and reflector can be mounted opposite each other across a gap.
NPN output and wiring check
The E3T-SR12 uses an NPN (sinking) output, switching the load to ground when the sensor is made.