LJ12A3-4-Z/BY PNP Inductive Proximity Sensor Switch DC 6V-36V NO 3-Wire 4mm
The LJ12A3-4-Z/BY is a 3-wire inductive proximity sensor designed for non-contact metal detection. It features an PNP transistor output with Normally Open (NO) logic, meaning the signal wire stays “Open” (High Impedance) until a metal object is detected within its 4mm range, at which point it pulls the signal to Ground (Sink).
Description:
Power supply reversal connection protection; short-circuit protection can directly connect with PLC
Used in common places with Medium environment resistance
Red LED indicates that it’s available to detect the sensor operation state
Economical and simple operation
Widely used, it can be a substitution for min-type switch and limit switch
IP 67 Water protection
Features:
Theory: Inductive Sensor.
High Repeated Positioning Accuracy.
Wire type and power: DC 3-wire type 6-36VDC
Sensing side diameter : M12
Sensing distance: 4mm
Installation: Non-Shield(non-flush)
Control output: PNP Normally Open
Specifications:
Types: LJ12A3-4-Z/BY
Mounting Hole Diameter: 12 mm
Detecting Distance: 4 mm
Working Voltage: 6-36V DC,
Current Output: 300mA
Output type: PNP, NO(Normally Open)
Weight: 40.8 g
Wiring & Pinout
The sensor typically follows a standard 3-wire color code:
Brown: Positive Supply (+VCC, 6-36V).
Blue: Negative/Ground (GND).
Black: Signal Output (PNP Sink).
Usage Tips
Microcontroller Connection: Because the sensor operates at a minimum of 6V, its signal output can damage 5V or 3.3V microcontrollers like Arduino. You should use a voltage divider or a zener diode to drop the black wire’s voltage to a safe level for your board.
Object Detection: Inductive sensors only detect conductive metals (iron, steel, aluminum, copper). Non-ferrous metals like aluminum will significantly reduce the effective sensing distance compared to iron.
Status Indicator: A red LED on the back of the sensor body provides immediate visual confirmation when a metal target is detected.








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