Product Overview
The 871TM-DH8CN18-H2 is a heavy-duty inductive proximity sensor from Allen-Bradley, part of Rockwell Automation’s 871TM all-stainless-steel tubular sensor family. Designed for non-contact detection of metallic targets in the most punishing industrial environments, the 871TM-DH8CN18-H2 combines an 18 mm threaded stainless steel barrel with a metal sensing face to deliver reliable performance where standard plastic-bodied sensors fail. Its 8 mm nominal sensing distance and unshielded (non-flush) mounting design make it a practical choice for position sensing, counting, and presence detection tasks on conveyors, cylinders, and machine fixtures.
The 871TM-DH8CN18-H2 operates on a 3-wire DC configuration with an NPN (sink) normally closed output, switching up to 200 mA at voltages between 10 and 30 VDC. The sensor’s internal oscillator generates a high-frequency electromagnetic field; when a ferrous metal target enters the field, eddy currents attenuate the oscillation, triggering the solid-state output. This contact-free principle eliminates mechanical wear, giving the 871TM-DH8CN18-H2 an effectively unlimited electrical life for high-cycle applications. Note that Rockwell has discontinued this model, making the 871TM-DH8CN18-H2 a sustainment item for existing installations.
The stainless steel construction of the 871TM-DH8CN18-H2 is its defining characteristic. The all-metal housing and face resist impact, abrasion, and corrosion far better than plastic alternatives, while full mechanical seals at all barrel openings and epoxy encapsulation protect internal circuitry from oils, coolants, and washdown. With an IP67 enclosure rating, the withstands dust ingress and temporary immersion, qualifying it for harsh manufacturing, automotive, and material handling environments.
Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 871TM- |
| Manufacturer | Allen-Bradley / Rockwell Automation |
| Product Type | Inductive Proximity Sensor, 3-Wire DC |
| Barrel Diameter | 18 mm (M18 × 1 thread) |
| Nominal Sensing Distance | 8 mm |
| Recommended Setting Distance | 0 to 6.5 mm |
| Shielding | Unshielded (non-flush mountable) |
| Output Configuration | NPN (Sink), Normally Closed (N.C.) |
| Operating Voltage | 10–30 VDC |
| Maximum Load Current | 200 mA |
| Switching Frequency | Up to 1,000 Hz |
| Connection Type | 2 m ToughLink cable, 3-conductor, 18 AWG |
| Enclosure Rating | IP67 |
| Housing Material | Stainless steel barrel and face |
| Operating Temperature | -25°C to +70°C |
| LED Indicator | Red LED, output status |
Main Features and Advantages
All-stainless construction for extreme durability: The is built with a one-piece stainless steel barrel and metal sensing face, a construction that resists impacts, abrasion, and chemical attack that would destroy plastic-bodied sensors. Mechanical seals at every barrel opening and full epoxy encapsulation protect the internal electronics from cutting fluids, oils, and moisture, ensuring long-term reliability in environments where sensor failure is not an option.
Optimized for ferrous metal detection: With a steel correction factor of 1.0, the delivers its full rated 8 mm sensing distance when detecting iron and steel targets, without the derating typically required for non-ferrous materials. This makes the particularly effective for detecting machine components, tooling, and fixtures made of ferrous metals in automotive and heavy equipment applications.
High switching frequency for dynamic applications: The achieves switching frequencies up to 1,000 Hz, enabling reliable detection in counting, speed sensing, and fast position feedback tasks. While not the fastest sensor in its class, this frequency is more than adequate for cylinder position, conveyor monitoring, and similar industrial automation functions where the is typically deployed.
Simplified integration with NPN sinking output: The provides an NPN normally closed output, the sinking configuration preferred by many PLC input modules and control systems. The 2-meter ToughLink cable offers flexibility for installation in confined spaces, and the integrated red LED provides immediate visual confirmation of output status for quick setup and troubleshooting.