Allen-Bradley 1746-FIO4I Analog Input/Output Module

Technical Dossier

Product Details And Specifications

Allen-Bradley SLC 500 (1746) Series Technical Notes

The Allen-Bradley SLC 500 platform, built on the 1746 backplane architecture, is one of the most widely deployed small-to-mid-range PLC systems in global heavy industry. Installed across petrochemical refineries, nuclear auxiliary systems, pulp and paper mills, water treatment facilities, and continuous process manufacturing plants, the SLC 500 series established a benchmark for modular, rack-based control architecture throughout the 1990s and 2000s. Its fixed and modular chassis configurations — ranging from 4-slot to 13-slot — support a dense ecosystem of discrete I/O, analog I/O, specialty, and communication modules, all sharing a common 1746 backplane bus. The platform's longevity in critical infrastructure means that demand for spare parts, including the 1746-FIO4I, remains active well beyond the series' mainstream production lifecycle.

The Evolution of SLC 500 (1746) Architecture

The SLC 500 family was introduced by Allen-Bradley (now Rockwell Automation) in the late 1980s as a successor to the SLC 100 and SLC 150 platforms. The 1746 backplane standard defined a parallel I/O bus that allowed processors and I/O modules to communicate at fixed scan rates, a design that prioritized determinism over bandwidth. Early processors such as the 1747-L20 and 1747-L30 offered limited memory and fixed I/O counts. Subsequent generations — the L40, L511, L514, L524, L531, L532, L541, L542, L543, and L553 — progressively expanded addressable I/O, program memory (from 1K to 64K words), and communication options.

The introduction of the 1746-FIO4I and related analog combination modules addressed the need for compact, mixed-signal control in space-constrained panels. The SLC 500 platform reached end-of-life (EOL) announcement from Rockwell Automation, with the recommended migration path toward the MicroLogix 1100/1400 and ultimately the CompactLogix 5370/5380 (1769 platform). However, the installed base remains extensive, and direct hardware replacement — rather than full system migration — is the preferred maintenance strategy for most facilities operating on fixed capital budgets.

SLC 500 (1746) Full Catalog & Functionalities — SKU List

Analog I/O Modules

• 1746-FIO4I: 2-ch analog input + 2-ch analog output, current mode (4–20 mA), combination module
• 1746-FIO4V: 2-ch analog input + 2-ch analog output, voltage mode (0–10 VDC), combination module
• 1746-NI4: 4-ch analog input, current/voltage selectable, 12-bit resolution
• 1746-NI8: 8-ch analog input, current/voltage selectable, 12-bit resolution
• 1746-NI16I: 16-ch analog input, current mode, high-density rack module
• 1746-NI16V: 16-ch analog input, voltage mode, high-density rack module
• 1746-NO4I: 4-ch analog output, current mode (4–20 mA), 12-bit resolution
• 1746-NO4V: 4-ch analog output, voltage mode (0–10 VDC), 12-bit resolution
• 1746-NR4: 4-ch RTD/resistance input module, supports Pt100, Pt1000, Ni120
• 1746-NT4: 4-ch thermocouple input module, supports J, K, T, E, R, S, B types
• 1746-NT8: 8-ch thermocouple input module, high-density temperature acquisition

Discrete I/O Modules

• 1746-IB16: 16-ch 24 VDC digital input module, sink type
• 1746-OB16: 16-ch 24 VDC digital output module, source type, 0.5 A per channel
• 1746-OW16: 16-ch relay output module, Form A contacts, 2 A per channel
• 1746-IA16: 16-ch 120 VAC digital input module
• 1746-OA16: 16-ch 120/240 VAC triac output module

CPU / Processor Modules

• 1747-L511: SLC 5/01 processor, 1K memory, DH-485 port
• 1747-L524: SLC 5/02 processor, 4K memory, DH-485 port
• 1747-L531: SLC 5/03 processor, 8K memory, RS-232 + DH-485
• 1747-L541: SLC 5/04 processor, 16K memory, DH+ port
• 1747-L553: SLC 5/05 processor, 64K memory, Ethernet/IP port

Communication & Specialty Modules

• 1746-BAS: BASIC module for custom ladder-integrated BASIC programming
• 1746-HSCE: High-speed counter/encoder module, up to 1 MHz input
• 1746-QS: Stepper/servo positioning module, single-axis
• 1747-SDN: DeviceNet scanner module for SLC 500 rack
• 1747-SCNR: Remote I/O scanner module, DH+ compatible

Quality Control for the SLC 500 (1746) Range

The 1746 backplane bus operates at a parallel TTL-level signal standard, making backplane connector integrity and bus timing critical to module reliability. DriveKNMS applies a multi-stage test protocol to all SLC 500 modules prior to shipment. Each module undergoes visual inspection for capacitor condition, connector pin integrity, and conformal coating status. Functional testing is performed in a live SLC 500 rack using a 1747-L553 processor running a dedicated diagnostic ladder program. For analog modules including the 1746-FIO4I, calibration verification is performed across the full 4–20 mA input and output range using a Fluke 725 multifunction process calibrator, with results logged to a per-unit test certificate. Communication modules are tested for scan list integrity and data table read/write accuracy under simulated network load.