1746-NR8 is an 8-channel RTD and resistance analog input module designed for the Allen‑Bradley SLC 500 PLC chassis platform, manufactured by Rockwell Automation. This module is officially discontinued, end-of-sale as of September 30, 2024, and serves as a critical spare for factories still operating legacy SLC 500 control systems where temperature monitoring via resistance temperature detectors is required. It accepts direct resistance inputs as well as multiple standard RTD types, converting measured resistance values into scaled engineering units for the SLC processor without external signal conditioning.

Each of the eight independent channels can be individually configured to output temperature in Celsius, Fahrenheit, or raw resistance in ohms. It supports 2-wire, 3-wire and 4-wire RTD hookups and provides built-in sensor break detection, overrange and underrange alarm status bits. Onboard filtering and high common-mode noise rejection make it suitable for temperature measurement in noisy industrial environments, including furnaces, reactors, dryers, pipelines and thermal process loops.

We supply visually inspected and functionally tested 1746-NR8 surplus and refurbished stock. Every unit is verified for chassis communication, channel response, terminal integrity and diagnostic LED operation before shipment. It is a direct drop-in replacement for existing SLC 500 racks and widely sourced for plant outage maintenance, spare part stocking and legacy automation retrofit.

Key Features

Allen‑Bradley 1746-NR8, 8-channel RTD / resistance analog input module for SLC 500 Supports platinum, nickel, copper and nickel‑iron RTD sensor types Individual channel configuration: °C, °F or raw ohm resistance output Compatible with 2-wire, 3-wire and 4-wire RTD wiring schemes Sensor open-circuit, short-circuit and out-of-range channel diagnostics 16-bit high-resolution conversion with user-selectable digital filters Selectable excitation current: 0.25 mA or 1.0 mA per channel Power-up auto-calibration plus periodic calibration option Minimum 120 dB 50/60 Hz common-mode noise rejection Removable terminal block for simplified wiring and replacement LED status indicators for module health and fault signalling Installs directly into standard SLC 500 I/O chassis Works with both fixed and modular SLC 500 processors Discontinued EOL spare part for legacy process temperature control

Product Specifications

Part number: 1746-NR8 Manufacturer: Allen‑Bradley / Rockwell Automation Platform: SLC 500 PLC Module type: RTD / Resistance Analog Input Channel count: 8 isolated input channels Supported RTD: Pt385, Pt3916, Cu426, Ni618, Ni672, NiFe518 Resistance ranges: 0–150 Ω, 0–300 Ω, 0–500 Ω, 0–1000 Ω, 0–3000 Ω Excitation: 0.25 mA or 1.0 mA software selectable Resolution: 16-bit Update rate: 6 ms to 125 ms per active channel, filter dependent Diagnostics: Broken sensor, overrange, underrange Noise rejection: Min 120 dB at 50 / 60 Hz with filter enabled Operating temperature: 0 °C to +60 °C Mounting: SLC 500 chassis backplane Backplane power draw: Supplied via SLC chassis End of sale: September 30, 2024, engineering replacement required for new builds

Typical Applications

Legacy SLC 500 process temperature monitoring Heat treatment furnace and oven temperature control Chemical reactor and batch vessel thermal measurement Oil and gas pipeline and tank farm temperature sensing Food & beverage thermal processing lines Power plant auxiliary equipment temperature logging Refinery and petrochemical plant legacy control spare replacement Water treatment and boiler temperature acquisition Industrial dryer, chiller and HVAC process monitoring SLC 500 system migration spare inventory

Why Choose Our 1746-NR8 Module

We specialise in hard-to-find Rockwell SLC 500 discontinued I/O spare parts for plant maintenance, system integrators and automation contractors. Since the 1746-NR8 is no longer available from official Rockwell sales channels, verified pre-tested stock is essential to avoid costly downtime for legacy temperature control loops. Each module undergoes channel functional testing, backplane communication check and terminal continuity validation before dispatch.

We can consolidate shipments alongside other SLC 500 spare parts such as processors, power supplies, digital and analog I/O cards. Commercial invoices, packing lists and test reports are available upon request. Tiered pricing is offered for bulk spare stocking and plant frame agreements. Send your full part list and required delivery schedule for a formal quotation.

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FAQ

Is 1746-NR8 still sold new by Rockwell? No. Rockwell officially discontinued the 1746-NR8 with last sale date September 30, 2024. It is only available as surplus, new old stock or tested refurbished spare.

Can I mix RTD types on the same module? Yes. Each of the eight channels can be independently configured for different RTD types or fixed resistance ranges in software.

Does this module support 4-wire RTD fully? It accepts 4-wire wiring but does not utilise the fourth sense wire for full 4-wire compensation; 3-wire is the most common wiring method for this card.

What is the migration replacement for 1746-NR8? Standard migration targets are Compact 5000 I/O RTD modules paired with Logix controllers. Replacement requires engineering rework, it is not a direct pin-for-pin substitute.

Will this work with all SLC 500 processors? It is compatible with fixed and modular SLC 500 processors including SLC 5/01, 5/02, 5/03, 5/04 and 5/05, installed in a standard SLC chassis.