The Omron E3T-ST12M is an active-production miniature through-beam photoelectric sensor with an NPN output, Dark-ON switching, and a fixed 1 m sensing distance. It operates on 12 to 24 VDC and comes pre-wired with a 2 m cable, which simplifies installation in compact automation cells or packaging machinery where space is tight. The NPN sinking output interfaces directly with standard PLC inputs that expect a current-sinking signal; the Dark-ON mode (D-ON) ensures the output activates when the beam is blocked, which is the typical configuration for part-presence detection.
The closest peer is the E3T-ST14, which shares the same sensing method, 1 m range, pre-wired cable, and dark-ON operation, but outputs PNP (sourcing) rather than NPN. If a panel was originally specified around the ST14 (PNP), dropping in the ST12M would require rewiring because the output polarity is opposite. Additionally, the ST14 includes output short-circuit protection and reverse-polarity protection—features absent from the ST12M per its spec sheet. Choose the ST12M when your input card is NPN and the load is resistive; the ST14 better suits sourcing inputs and environments where short-circuit protection at the sensor terminal is valued.
Mount the rectangular compact body in a right-angle orientation; the 2 m pre-wired cable reaches typical bracket positions without an extension. The 1 m through-beam range demands clean line-of-sight alignment between transmitter and receiver, with no obstructions within the cone. Power at 12–24 VDC with less than 10% ripple; the NPN collector output sinks up to 50 mA. For inductive loads, add a flyback diode across the load—the sensor does not include internal suppression. Red LED indicator confirms beam status during setup.