The LJ8A3-2-Z/AX M8 2mm Inductive Proximity Sensor (NPN Normally Closed / 6–36V DC / 200mA) is a rugged, industrial-grade non-contact position detection sensor designed for precision automation, metal sensing, and limit switching. Housed in a nickel-plated brass M8 threaded barrel with an IP67 environmental protection rating, it features an effective detection distance of 2 mm for ferrous metal targets (such as iron and steel). Operating on a wide 6V to 36V DC supply voltage, it utilizes an NPN Normally Closed (NC) 3-wire transistor output capable of sinking up to 200 mA directly to relays, PLC digital inputs, counters, or microcontroller interfaces. It is widely utilized in CNC machinery limit sensing, 3D printer auto-bed leveling, industrial conveyor part counting, speed monitoring, and robotics position sensing.

Specifications

• Model / Part Number: LJ8A3-2-Z/AX (M8 Inductive Proximity Switch)
• Sensor Type: Inductive Proximity Sensor (Eddy Current Metal Detection)
• Housing / Barrel Size: M8 Metric Thread (8 mm Diameter)
• Mounting Type: Shielded / Flush Mount
• Detection Distance (Sn): 2.0 mm ± 10%
• Reliable Sensing Distance (Sa): 0 to 1.6 mm
• Standard Target Object: Iron / Mild Steel (8 mm × 8 mm × 1 mm)
• Detectable Targets: Ferrous and Non-Ferrous Metals (Iron, Steel, Copper, Aluminum, Brass; non-ferrous metals have a reduced sensing distance)
• Output Type: NPN Transistor Open-Collector (Current Sinking)
• Switching State / Logic: NC (Normally Closed – Output is conducting/LOW when NO target is detected, opens/HIGH-Z when target is present)
• Operating Supply Voltage: 6V to 36V DC (Typ. 12V / 24V DC systems)
• Maximum Output Load Current: Up to 200 mA (Continuous sink current)
• Current Consumption: ≤ 10 mA (at 24V DC unloaded)
• Output Voltage Drop (V_d): ≤ 1.5 V (at 200 mA load)
• Switching Response Frequency: Up to 1.0 kHz (1000 Hz)
• Hysteresis / Differential Travel: ≤ 10% of sensing distance
• Status Indicator: High-Visibility Red/Amber LED (Illuminates when target is detected / state changes)
• Internal Circuit Protections: Reverse-polarity protection, surge voltage suppression, and output short-circuit protection
• Ingress Protection Rating: IP67 (Dust-tight and water immersion resistant)
• Housing Material: Nickel-Plated Brass Body with Blue/Orange PBT Plastic Sensing Face
• Operating Ambient Temperature: -25°C to +70°C
• Cable Length & Type: Approx. 1.0 to 1.2 Meters, 3-Core PVC Insulated Cable
• Wiring Color Code (Standard 3-Wire DC):
  • Brown (BN): Power Supply Positive (+6V to +36V DC / V_CC)
  • Blue (BU): Power Supply Ground (0V / GND)
  • Black (BK): Signal Output (NPN NC - Connects to Load / Controller Input)
• Overall Dimensions: M8 × 1.0 mm Thread, Length approx. 50 mm (Threaded section approx. 40 mm)
• Weight: Approx. 35 g (including cable and mounting nuts)

Features

• Non-Contact Solid-State Sensing: Detects metallic objects without mechanical contact, eliminating mechanical wear, bounce, and friction for over millions of reliable cycles.
• Normally Closed (NC) Fail-Safe Logic: Provides continuous active circuit continuity until a target is encountered or a wire is broken, making it ideal for safety limit stops and endstops.
• Wide 6V–36V Operating Voltage: Compatible with industrial 24V PLC automation systems, 12V automotive/CNC supplies, and 9V battery systems.
• High Switching Frequency (1 kHz): Capable of high-speed rotation tracking, pulse generation, and rapid part counting on conveyor belts.
• IP67 Industrial Ingress Protection: Rugged sealed body resists cutting fluids, machine oil, moisture, coolant splashes, and heavy workshop dust.
• Complete Mounting Hardware: Includes two M8 nickel-plated hex nuts and a tooth lock washer for rigid, vibration-resistant positioning.

Common Applications

• CNC Milling & Lathe Limit Stops: X/Y/Z-axis homing, hardware over-travel protection, and tool positioning detection.
• 3D Printer Bed Leveling: Metal heated bed sensing and Z-probe height compensation for reprap and custom 3D printers.
• Industrial Automation & PLCs: Direct digital input triggering for 24V PLC controllers (Siemens, Delta, Mitsubishi, Omron).
• RPM & Speed Measurement: High-speed pulse counting on rotating metal gears, motor shafts, and sprockets.
• Conveyor Object Sorting: Detecting the presence or absence of metal cans, parts, or brackets on factory conveyor lines.

Usage Tips

• NPN (Current Sinking) Interfacing: The black output wire acts as an open-collector switch that pulls down to Ground (Blue wire). To interface with a 5V/3.3V microcontroller (Arduino, ESP32, STM32):
  • Power the sensor with at least 6V to 12V DC (do not power directly from 5V as it falls below the minimum operating threshold).
  • Connect the Black wire to the microcontroller GPIO input pin.
  • Enable the microcontroller's internal pull-up resistor (or place an external 4.7kΩ to 10kΩ pull-up resistor between the GPIO pin and the microcontroller's 3.3V/5V V_{CC} rail). Because the NPN output only sinks to Ground, the GPIO pin is safely protected from the sensor's higher supply voltage.
• Material Correction Factors: The nominal 2 mm sensing distance applies to mild steel/iron (correction factor = 1.0). For other metals, multiply the sensing distance accordingly:
  • Stainless Steel: ~0.7 to 0.8 × (Approx. 1.4 mm – 1.6 mm)
  • Brass: ~0.4 to 0.5 × (Approx. 0.8 mm – 1.0 mm)
  • Aluminum / Copper: ~0.3 to 0.4 × (Approx. 0.6 mm – 0.8 mm)
• Shielded Flush Mounting: Because the M8 barrel is shielded, the sensor face can be mounted flush with surrounding metal plates without false triggering from surrounding metal frames.
• Direct Load Driving: The sensor can drive small 12V/24V DC relays, buzzer indicators, or solenoid valves directly (up to 200mA). When driving inductive loads, place a freewheeling diode (e.g., 1N4007) across the relay coil.