What this sensor is and what it does
The Omron E3JK-5M1-N is a through-beam photoelectric sensor in a block-style housing. It uses an infrared LED light source at 950 nm and a separate receiver to detect an opaque object of at least 14.8 mm diameter breaking the beam at up to 5 m. The output is a relay rated for 0 to 3 A load current, so it can switch small motor contactors, solenoid valves, or indicator lamps directly without an interposing relay.
Deployment context
This sensor is a block-style unit — it bolts to a bracket or machine frame, not a DIN rail. The through-beam pair (emitter and receiver) needs clear line-of-sight across a gap up to 5 m. The relay output means it can handle the inrush of a small motor starter or a panel indicator without a separate solid-state interface. Out here in the grease, that relay output is a plus — it's tougher than a transistor output if you get a voltage spike from an adjacent motor start.