Capacitance Proximity Sensor LJC18A3-B-Z/AX

The LJC18A3-B-Z/AX Capacitive Proximity Sensor is a professional-grade industrial sensor designed to detect the presence of objects without any physical contact. Unlike inductive sensors that only detect metal, this capacitive sensor can detect virtually any material — including metals, plastics, glass, ceramics, wood, paper, water, oil, and other liquids — making it one of the most versatile proximity sensors available.

The sensor works by generating an electrostatic field at its sensing face. When an object enters this field, it alters the capacitance of the sensor's internal oscillator, which the sensor's electronics detect and convert into a digital switching signal. The detection distance varies depending on the conductivity, dielectric constant, water content, and volume of the target material, with the maximum detection distance achieved for grounded metal objects.

Housed in a robust 18 mm diameter cylindrical metal body with a threaded barrel, this sensor is easy to mount in machinery, tanks, conveyors, or custom enclosures using standard locking nuts. The detection range is adjustable from 1 mm up to 10 mm, allowing precise tuning for your specific application.

The sensor outputs an NPN Normally Closed (NC) signal through a 3-wire cable approximately 0.6 meters long, and operates over a wide voltage range of DC 6V to 36V, making it compatible with most industrial control systems, PLCs, Arduino, ESP32, Raspberry Pi (with level shifting), and microcontroller-based automation projects.

Specifications

• Model: LJC18A3-B-Z/AX (also available as LJC18A3-H-Z/AX)
• Sensor Type: Capacitive Proximity Sensor
• Detection Method: Capacitance change
• Detection Range: 1 mm to 10 mm (adjustable)
• Detectable Materials: Metal, plastic, glass, water, oil, wood, ceramics, paper, liquids
• Operating Voltage: DC 6V – 36V
• Output Current: Up to 300 mA
• Output Type: NPN, 3-Wire, Normally Closed (NC)
• Housing Diameter: 18 mm cylindrical (threaded)
• Cable Length: Approximately 0.6 meters (60 cm)
• Wire Configuration:
  • Brown → Positive Supply (V+)
  • Blue → Ground (V−)
  • Black → Signal Output (NPN NC)
• Mounting: Threaded barrel with locking nuts
• Construction: Metal housing with plastic sensing face
• Adjustment: Sensitivity adjustment potentiometer (rear of sensor)
• Manufacturer: Shande Electric Factory

Wiring Guide

Note: For use with Arduino or 3.3V/5V microcontrollers, a pull-up resistor (typically 10 kΩ to V+) is required on the output line, and the signal must be scaled down to a safe input voltage. The NPN open-collector output pulls the line LOW when no object is detected (normally closed) and releases the line when an object enters the detection zone.

Applications

• Liquid Level Detection – Detect water, oil, or other liquids through tank walls (non-metallic tanks)
• Tank & Bottle Filling Systems – Automated bottling and packaging
• Object Presence Detection – Verify parts on conveyors and assembly lines
• Material Handling – Count or detect packages, boxes, and bags
• Pet Feeders & Smart Bowls – Detect food or water levels
• Industrial Automation – Replace mechanical limit switches with non-contact sensing
• Flour, Grain, and Powder Level Detection – Granular material level control
• Coffee Machines & Vending Machines – Detect liquid and cup presence
• Glass & Plastic Manufacturing – Detect non-metallic products on production lines
• Smart Home Automation – Touchless switches and presence sensing
• PLC & Industrial Control Systems – Direct compatibility with industrial logic controllers
• Arduino & Maker Projects – Versatile DIY automation sensor
• Robotics – Non-contact obstacle and material detection
• Aquariums & Hydroponics – Monitor water levels in growing systems
• Anti-Tamper & Security Systems – Detect material presence in protected zones