Allen-Bradley 1746-NIO4I: SLC 500 Analog I/O Module

Name: Allen-Bradley 1746-NIO4I: SLC 500 Analog I/O Module
Brand: Allen-Bradley

Model: 1746-NIO4I

Brand Allen-Bradley

Series SLC 500

Model 1746-NIO4I

RFQ-ready model route Obsolete and surplus sourcing Export follow-up by model list

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Technical Dossier

Product Details And Specifications

Allen-Bradley 1746 Series Technical Notes

The Allen-Bradley 1746 series constitutes the I/O subsystem of the SLC 500 programmable controller platform, one of the most widely deployed mid-range PLC architectures in global heavy industry. Installed across petrochemical refineries, nuclear auxiliary systems, pulp and paper mills, automotive assembly lines, and water treatment facilities, the 1746 I/O chassis and module ecosystem represents decades of field-proven reliability in environments demanding continuous 24/7 operation.

The 1746-NIO4I is a combination analog input/output module providing 4 analog inputs and 2 analog outputs in a single slot, supporting current (4–20 mA) and voltage (0–10 VDC / ±10 VDC) signal ranges. It interfaces directly with the SLC 500 backplane via the 1746 chassis (4, 7, 10, or 13-slot variants) and is programmed through RSLogix 500 / Studio 5000 Logix Designer in legacy compatibility mode.

The Evolution of 1746 Architecture

The SLC 500 platform was introduced by Allen-Bradley (now Rockwell Automation) in the late 1980s as a modular successor to the fixed SLC 100/150 controllers. The 1746 I/O family was designed to provide slot-addressable, rack-local I/O for the SLC 5/01 through SLC 5/05 processors housed in 1747-series chassis.

Early 1746 modules (circa 1990–1998) used parallel backplane communication with fixed addressing. The architecture matured through the 1990s with the introduction of higher-density analog modules, thermocouple/RTD inputs, and specialty function modules. By the mid-2000s, the SLC 500 / 1746 platform entered its mature phase as Rockwell transitioned customers toward the ControlLogix (1756) and CompactLogix (1769) platforms.

As of 2024, Rockwell Automation has formally announced end-of-life for multiple 1746 catalog numbers. The 1746-NIO4I and many peer modules are now in the discontinued / last-time-buy lifecycle phase, making third-party spare parts sourcing the primary supply channel for maintenance operations. Compatibility with existing SLC 500 chassis and processors remains unchanged — no firmware migration is required when replacing like-for-like modules.

1746 Series Full Catalog & Functionalities (SKU List)

Analog Input Modules

1746-NI4: 4-channel analog input, current/voltage selectable per channel, 12-bit resolution
1746-NI8: 8-channel analog input, current/voltage, 12-bit, single-ended
1746-NI16I: 16-channel isolated analog input, 4–20 mA, 12-bit resolution
1746-NI16V: 16-channel analog voltage input, 0–10 VDC / ±10 VDC, 12-bit
1746-NT4: 4-channel thermocouple/mV input module, types J/K/T/E/R/S/B/N
1746-NR4: 4-channel RTD/resistance input, PT100/PT1000/Ni/Cu, 16-bit

Analog Output Modules

1746-NO4I: 4-channel isolated analog current output, 4–20 mA, 12-bit
1746-NO4V: 4-channel analog voltage output, 0–10 VDC / ±10 VDC, 12-bit
1746-NO8I: 8-channel analog current output, 4–20 mA, non-isolated
1746-NO8V: 8-channel analog voltage output, 0–10 VDC, non-isolated

Combination Analog I/O Modules

1746-NIO4I: 4 analog inputs + 2 analog outputs, current/voltage, 12-bit — this module
1746-NIO4V: 4 analog inputs + 2 analog voltage outputs, 12-bit resolution

Digital Input Modules

1746-IA16: 16-channel 120 VAC digital input module, screw terminal
1746-IB16: 16-channel 24 VDC sinking digital input module
1746-IB32: 32-channel 24 VDC sinking digital input, high-density

Digital Output Modules

1746-OA16: 16-channel 120/240 VAC triac output module
1746-OB16: 16-channel 24 VDC sourcing transistor output
1746-OW16: 16-channel relay output, Form A, 240 VAC / 24 VDC

Specialty / Communication Modules

1746-BAS: BASIC language module for custom ladder-integrated programming
1746-HSCE: High-speed counter encoder module, 1 MHz input rate
1746-QS: Stepper/servo positioning module, single-axis open-loop control

Sourcing Hard-to-Find & Obsolete 1746 Series Parts

With Rockwell Automation having discontinued active production of the majority of 1746 catalog numbers, the global installed base — estimated in the hundreds of thousands of SLC 500 racks — depends entirely on the secondary market and specialist distributors for corrective and preventive maintenance.

Surplus sourcing options from verified OEM overstock channels
Refurbished units with full functional restoration to factory specification
Cross-reference identification for equivalent replacement modules where direct substitution is not available
Emergency urgent RFQ handling for critical plant shutdown scenarios

For plants operating SLC 500 systems beyond their original design life, DriveKNMS provides lifecycle extension consultation, including assessment of migration paths to CompactLogix 5380 (1769-L3x) with 1746 I/O adapter bridges where applicable.

Quality Control for the 1746 Series Range

The 1746-NIO4I and all analog modules in the 1746 family undergo a structured multi-stage test protocol at DriveKNMS prior to dispatch:

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