Overview
The Allen-Bradley 871L-B20E40-T2 is a limit switch-style inductive proximity sensor engineered for non-contact detection of metal objects in industrial automation systems. As part of the Bulletin 871L series, this sensor provides a non-contact alternative to NEMA-style limit switches, using the same footprint as traditional limit switches for mounting interchangeability, easily-wired terminations and rugged construction. The sensor features a 40 mm head size, 20 mm sensing distance, shielded design, and selectable Normally Open/Normally Closed outputs with 1/2 inch NPT internal threads.
Key Features
- 20mm Sensing Distance: Provides reliable detection range for precise object positioning without physical contact
- Shielded Design: Minimizes electromagnetic interference from surrounding metal objects for consistent performance
- 2-Wire AC/DC Configuration: Simplifies installation and wiring, while selectable Normally Open (N.O.) or Normally Closed (N.C.) output offers flexibility to meet varying application requirements
- Drop-in Limit Switch Replacement: Mounts directly in traditional limit switch locations without mechanical redesign
- 40mm Head Size: Compact form factor suitable for confined spaces and standard industrial equipment
- 1/2-inch NPT Conduit Entry: Industry-standard threaded connection for secure conduit mounting
Technical Specifications
- Sensing Distance: 20 mm (0.79 in.)
- Operating Voltage: 20–250V AC/DC
- Head Size: 40 mm
- Output Configuration: Selectable N.O. / N.C.
- Switching Frequency: 15 Hz
- Connection Type: Conduit style with 1/2 in. NPT internal threads
- Shielding: Yes (reduces side sensing)
- Catalog Number: 871L-B20E40-T2
Typical Applications
The 871L-B20E40-T2 is ideal for manufacturing and process control environments where non-contact sensing is required:
- Conveyor system object detection and position sensing
- Assembly line limit detection and part sorting
- Machine tool position indication and safety interlocks
- Packaging and material handling systems
- Industrial automation and motion control systems
- Equipment protection and overtravel detection
Compatibility & Replacements
Compatible With
- Allen-Bradley control systems and PLCs
- Rockwell Automation industrial automation platforms
- Standard industrial 20–250V AC/DC circuits
- Legacy limit switch-based machine designs
- NEMA 4/4X/12 enclosures and control panels
Replaces / Drop-In Replacement For
The 871L-B20E40-T2 uses the same footprint as traditional limit switches, providing mounting interchangeability for easy retrofit of existing equipment. Consult your equipment documentation or contact your system integrator for specific legacy model numbers requiring replacement.
Works With
- AC/DC control circuits and relay logic systems
- PLC analog input modules (with appropriate signal conditioning)
- Safety-rated control systems (verify compliance with your application)
- Industrial cordsets and connectors (standardQuick Disconnect or conduit-threaded options)
