Product Overview

The Allen Bradley 1746-NR8 operates as a high-density, 8-channel RTD and resistance analog input module designed explicitly for the legacy SLC 500 programmable logic controller platform. This open-style chassis card translates low-voltage resistance variations from field temperature sensors into precise digital values for the central SLC processor. Although the original manufacturer designated this model as a legacy item, we supply this product exclusively as a 100% brand new, original unit in its authentic factory box to guarantee immediate replacement compatibility and long-term asset lifecycle expansion.

Technical Specifications

Engineering Advantages

Food processing facilities, chemical plants, and heavy thermal energy networks require exceptionally stable temperature monitoring to maintain process safety and batch consistency. The 1746-NR8 addresses these processing demands by providing 8 high-accuracy input channels within a single slot footprint, allowing engineers to maximize slot utilization inside standard SLC 500 chassis. The module supports multiple selectable resistance ranges (0 to 500, 1000, and 3000 Ohms) to match Pt100, Ni100, and Cu100 RTD physical characteristics without needing external signal conditioning transducers.

The hardware utilizes an advanced channel filtering design that rejects common high-frequency electromagnetic interference (EMI) originating from large induction motors and nearby variable frequency drives (VFDs). A robust continuous isolation barrier rated for 50 V defends the internal backplane bus against stray field ground loops, preventing field electrical noise from corrupting data on the primary processor.

To accelerate field installation and maintenance cycles, the module features a removable 1746-HT wiring terminal block. Field technicians can swap a compromised input card out of the rack without loosening individual sensor signal wires, entirely eliminating rewiring errors and cutting downtime.

FAQs

• Can technicians mix different types of RTD sensors across the 8 channels of a single 1746-NR8 module?

  Yes. The software configuration tools within RSLogix 500 allow independent channel definition. Maintenance teams can configure Channel 0 for a Pt100 sensor while assigning Channel 1 to a direct Ohm resistance sensor or a different RTD element type, maximizing local flexibility.

• What specific diagnostic steps help isolate a sensor wiring issue from an internal card hardware fault?

  The 1746-NR8 communicates granular diagnostic bits directly to the SLC 500 controller data table. An open-circuit or short-circuit condition on the field wiring triggers a specific under-range or over-range bit for that exact channel, enabling operators to identify broken wires on the factory floor without pulling the module from the chassis.

• Does this module draw power directly from an external 24 VDC power supply terminal line?

  No. The 1746-NR8 derives all required operational voltages directly from the standard SLC 500 backplane power supply bus, consuming 150 mA at 5 VDC. This self-contained layout eliminates the need to route extra external power loops to the card, reducing cabinet wiring clutter.