LJ18A3-8-J/DZ / R18-8A2 Inductive Proximity Sensor NC, DC 6–36V, 300mA, 6.4mm Detection Range

This LJ18A3 model is Normally Closed (NC). In its idle state (no target present), the output transistor is ON, providing a closed circuit to the load. When a metal target enters the 6.4mm sensing range, the output switches OFF, opening the circuit. This configuration is often used for fail-safe applications where an open circuit indicates a fault or detection event.

The sensor operates on a wide DC voltage range of 6 to 36V. It includes reverse polarity protection, but you must ensure the power supply can deliver the required current (up to 300mA max) and is stable. It is compatible with common 12V or 24V industrial DC power systems and PLC input modules.

No. Standard inductive proximity sensors like the LJ18A3 series are specifically tuned to detect ferrous metals (iron and steel). The sensing distance is reduced or may be non-existent for non-ferrous metals. For aluminum or copper detection, a capacitive or specialized non-ferrous inductive sensor is required.

The sensor has three wires: Brown (V+), Blue (V- / Ground), and Black (Signal Output). Connect Brown to your DC positive supply (6-36V), Blue to DC negative/ground. The Black wire is the switched NPN output. Connect it to your PLC input or load, which must be connected back to the positive supply (sourcing input) for the NC switching action to function correctly.

A non-shielded sensor allows the magnetic field to extend to the sides of the barrel. This means it can be installed flush with a metal mounting surface without a loss of sensing range. However, non-shielded sensors require more clearance from adjacent metal objects (typically 2x the sensor diameter) to prevent false triggering.