LJ18A3-8-Z-BX 8mm Inductive Proximity Sensor

LJ18A3-8-Z-BX 8mm Inductive Proximity Sensor
LJ18A3-8-Z-BX 8mm Inductive Proximity Sensor
LJ18A3-8-Z-BX 8mm Inductive Proximity Sensor
  • LJ18A3-8-Z-BX 8mm Inductive Proximity Sensor
  • LJ18A3-8-Z-BX 8mm Inductive Proximity Sensor
  • LJ18A3-8-Z-BX 8mm Inductive Proximity Sensor

LJ18A3-8-Z-BX 8mm Inductive Proximity Sensor

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  • Photo Sensor Switch for sense reflecting target in 300 mm sensing range with 2m cable
  • With short-circuit protection and inverted connecting protection.
  • High precision of repeated location.
  • Has an operating voltage range of 10-35 VDC
  • Features Red LED indicator show status.
  • Good performance of anti-interference.

8mm Inductive Proximity Sensor

The LJ18A3-8-Z/BX proximity sensor will detect large metal fields at an 8mm distance with great precision. This allows you to accurately measure the distance to an (aluminum) heated bed for example. If you are using a glass plate as your print surface, you can use aluminum foil right below the glass, which will also be detected by the sensor (mirrors however are not detected). The sensor is equipped with a small red detection LED, indicating a nearby object. The sensor has M18 threading and includes a nut for easy mounting to your 3D printer or CNC machine.

The LJ18A3 is a PNP Normally Open (NO) type of proximity sensor. This means that the signal lead will output a positive voltage (same as the input voltage) when a metal mass is detected. When nothing is detected, the signal is equal to ground.

Most modern 3D printer firmware has some sort of auto bed leveling procedure available, but you will need to enable it. You can use this sensor as the z_min_endstop for example, replacing your current end stop. Most firmware will also use the min end stop as a probe, but some allow a separate probe to be defined.

This sensor operates at 6-36V, so as the signal voltage is the same as the input voltage, also the signal will be 6-36V. You will need to down-convert the voltage to an acceptable level for your electronics. Please see the linked schematic on how to connect this sensor to the end stop pins of your electronics board.


  • Wire - red or brown - supply voltage - V 5
  • Wire - green or blue - ground - GND
  • Wire - yellow or black - digital output - OUT
    • there is no object - high status
    • the object detection - low status


  • Mine metallurgy.
  • Plastics, textile, and Chemical Industry.
  • Light industry, tobacco, electric power, railway, and war industry.

Package Includes:

  • 1 x Inductive Proximity Switch

Inductive Proximity Sensor Specification

Diameter of Head 18mm
Detecting Distance 8mm
Supply Voltage DC 6-36V
Current Output 300mA
Detect Object Iron
Cable Length 103cms
Dimensions  7 x 3 cms
Weight  100 grams


Frequently Asked Questions

1. What is LJ18A3-8-Z/BX sensor?

  • LJ18A3-8-Z/BX 8mm Approach Sensor RM18 DC6~36V (Unshielded) is a brand new inductive proximity sensor that detects a metal object with a maximum distance of 8mm from the sensor. The sensor has 3 wire and NO (Normally open) type output with RED LED indicator.

2. What is a inductive proximity sensor?

  • A inductive proximity sensor can detect metal targets approaching the sensor, without physical contact with the target. Inductive Proximity Sensors are roughly classified into the following three types according to the operating principle: the high-frequency oscillation type using electromagnetic induction, the magnetic type using a magnet, and the capacitance type using the change in capacitance.

3. How does inductive proximity sensor work?

  • Inductive Proximity Sensors detect magnetic loss due to eddy currents that are generated on a conductive surface by an external magnetic field. An AC magnetic field is generated on the detection coil, and changes in the impedance due to eddy currents generated on a metallic object are detected.
    Other methods include Aluminum-detecting Sensors, which detect the phase component of the frequency, and All-metal Sensors, which use a working coil to detect only the changed component of the impedance. There are also Pulse-response Sensors, which generate an eddy current in pulses and detect the time change in the eddy current with the voltage induced in the coil.