Application Scenarios
Picture a chemical batch reactor where the SLC 5/04 processor’s PID loop calculates a control output every scan, but the control valve positioner, the cooling-water VFD, the steam-control I/P converter, and the pH reagent pump all demand their own independent 4–20 mA command signals. A discrete output module cannot represent “43% open” — it can only say on or off. The 1746-NO4I bridges that gap: four dedicated current outputs, each sourced from the same processor word but driving completely independent loops. When the processor transitions to PROGRAM or FAULT mode, all four outputs automatically force to 0 mA — a deliberate safe-state design that drives the valve closed, the VFD to minimum speed, and the reagent pump to zero flow. This isn’t just convenient; it’s the kind of fail-safe behavior that keeps a batch reactor from over-pressurizing when a technician opens the program online.
Parameter
| Main Parameters | Value / Description |
|---|---|
| Product Model | 1746-NO4I (also referenced as 1746-NO4I, Series A = Rev A) |
| Manufacturer | Allen-Bradley / Rockwell Automation |
| Product Category | Analog Current Output Module |
| Product Family | SLC 500 1746 Modular I/O |
| Number of Outputs | 4 current output channels (non-isolated from each other; share ANL COM) |
| Output Signal Type | Current (I = Current; voltage version is separate 1746-NO4V) |
| Output Range (Normal) | 0 to +20 mA DC per channel |
| Full-Scale Output | 0 to +21 mA (5% overrange capability, –1 LSB) |
| Output Coding | 0 to +32,764 counts = 0 to 21 mA |
| Data Format | 16-bit two’s complement binary |
| Converter Resolution | 14-bit (effective) |
| Resolution per LSB | 2.56348 µA per LSB |
| Conversion Method | R-2R ladder DAC |
| Update Time | 512 µs for all 4 channels in parallel |
| Step Response | 2.5 ms (5% to 95% of final value) |
| Load Range | 0 to 500 Ω per channel |
| Maximum Load Reactance | 100 µH |
| Backplane Current (5V DC) | 55 mA |
| Backplane Current (24V DC) | 195 mA (when powered from backplane) |
| External 24V DC Option | 24V ±10% (21.6 to 26.4V DC) via onboard SW1 switch; reduces backplane loading |
| Backplane Isolation | 500V AC and 710V DC @ 1 minute (field wiring to backplane) |
| Accuracy @ 25 °C | ±0.298% of full scale |
| Accuracy (0–60 °C) | ±0.541% of full scale |
| Accuracy Drift | ±70 ppm/°C of full scale |
| Power Status LED | Indicates when backplane power is active |
| Terminal Block | Removable 18-point screw-terminal block (1746-RT28 style) |
| Chassis Compatibility | 1746-A4, A7, A10, A13 (single slot); fixed SLC 500 chassis also supported |
| Processor Compatibility | SLC 5/01, 5/02, 5/03, 5/04, 5/05 |
| Programming Software | RSLogix 500 (Output data file O: word, e.g., O:6.0–O:6.3 for slot 6) |
| Recommended Cable | Shielded Belden #8761 (or equivalent); max wire size #14 AWG |
| Operating Temperature | 0 °C to +60 °C (32 °F to 140 °F) |
| Storage Temperature | -40 °C to +85 °C (-40 °F to 185 °F) |
| Relative Humidity | 5% to 95%, non-condensing |
| Dimensions (H × W × D) | 14 × 3.5 × 14.5 cm (5.5 × 1.4 × 5.7 in) |
| Weight | 0.34 kg (0.75 lbs) |
| Certifications | UL Listed, CSA, CE (per SLC 500 family certification) |
| Lifecycle Status | Discontinued — Rockwell Automation ceased sales April 29, 2021; available through new-surplus, refurbished, and repair channels |
