B-Line E51ALS120 E51 Series, Limit Switch Style, Modular Inductive Proximity Sensor

Output is a solid state 500 mA AC/DC, short circuit protected. That's enough for a PLC input, a small pilot light, or a control relay coil, but it will not drive a motor starter coil or contactor above 500 mA. For anything heavier, switch an interposing relay with the sensor and let the relay carry the load.

The E51ALS120 is rated NEMA 3, 3S, 4, 4X, 6, 6P, 12 and 13, plus IP67. That covers rain, hosedown, dust, oil and temporary submersion, and the 4X rating means corrosion resistance. The receptacle and housing are die cast zinc with a plastic sensing head. Working range is -13 to 158 F (-25 to 70 C), so it is not a freezer-aisle or high-heat-oven device.

Metal only. It is an inductive proximity sensor, so it senses ferrous and other conductive metal targets and ignores plastic, cardboard, glass and liquids. If you need to detect non-metallic product, you want a photoelectric or capacitive sensor instead.

Shielded operating mode means the sensing field is focused out the front face, so the sensor can be mounted flush in a metal plate or bracket without the surrounding steel triggering it. That is the usual choice for machine-guard and tooling mounts. Unshielded sensors reach farther but need a clear non-metal ring around the face.

Two LEDs on the E51ALS120 tell you where the fault sits: green confirms the sensor has power, yellow shows output status. Green on with no yellow when the target is in front means the sensor is live but not seeing the target, so check target material, gap and alignment. No green at all sends you back to the supply and the screw terminal connections.

Allow for a body measuring 4.53 x 1.78 x 1.54 inches (height x width x length) and roughly a pound of weight, so bracket it rather than letting the cable carry it. The limit switch style body is meant to drop into the same kind of mounting position a mechanical limit switch occupied on the machine.

Repeat accuracy is better than 0.3 percent, which is fine for position, end-of-travel and part-present detection on conveyors, presses and indexing tooling. It is a switching sensor, not a measuring device, so it tells you the target is there, not how far away it is.

Order by manufacturer part number E51ALS120, from the Eaton B-Line E51 Series. It is the modular, limit switch style inductive proximity unit with the 20 to 264V AC/DC, 2-wire normally open configuration, so quote that MPN exactly rather than a generic E51 reference.