Overview
The Allen-Bradley 1746-NO4I is a four-channel analog output module for the SLC 500 product family. This non-isolated output module provides current-loop signals (0–20 mA) for controlling proportional valves, analog drives, instrumentation, and other devices requiring precise analog command signals. The 1746-NO4I integrates directly into any standard SLC 500 rack with screw-terminal connections for simplified wiring and maintenance.
Key Features
- Four independent analog current outputs (0–20 mA range with 21 mA over-range capability)
- 14-bit digital-to-analog converter resolution via R-2R ladder network
- Selectable power source: backplane 5V DC or external 24V DC ±10%
- Fast step response of 2.5 milliseconds at 95% settling
- Removable terminal blocks for convenient module replacement and field wiring
- LED status indicator for diagnostics
Technical Specifications
- Output Channels: Four (4) analog current outputs
- Output Range: 0 to 20 mA (21 mA over-range at 5% over-scale)
- Resolution: 14 bits, 2.56348 µA per LSB
- Data Format: 16-bit two’s complement binary
- Backplane Current Draw: 55 mA @ 5V DC; 195 mA @ 24V DC (external)
- External Power Supply: 24V DC ±10% at 195 mA maximum (NEC Class 2 required)
- Step Response: 2.5 milliseconds @ 95% settling
- Load Impedance: 0–500 Ω; maximum reactance 100 µH
- Accuracy Drift: ±70 ppm/°C of full-scale
- Operating Temperature: 0 to 60°C
- Storage Temperature: –40 to 85°C
- Humidity: 5 to 95% non-condensing
- Isolation: Non-isolated (500V DC backplane isolation)
- Terminal Style: Screw terminals
- Mounting: Rack mount (SLC 500 fixed or modular chassis)
- Weight: 0.44 lbs
Typical Applications
The 1746-NO4I is widely deployed in process control, machine automation, and motion control environments where analog output signals drive proportional devices:
- Proportional valve command signals (hydraulics, pneumatics)
- Variable frequency drive (VFD) speed references
- Analog instrumentation and transducer signal outputs
- PID controller analog output (CO) for closed-loop control
- Signal re-transmission and data logging applications
- Manual command input for operator-controlled loading stations
Compatibility & Replacements
The 1746-NO4I is discontinued by the manufacturer but remains in active service across legacy SLC 500 systems. This module mounts directly into any SLC 500 rack (fixed or modular) and is compatible with SLC 5/01, 5/02, 5/03, and 5/04 processors. Common similar modules include the 1746-NO4V (voltage output variant) and the 1746-NO8I (eight-channel version). For new designs, Rockwell recommends CompactLogix or ControlLogix platforms, but sourcing used 1746-NO4I modules remains cost-effective for plant modernization and system repairs. When installing, position the module away from high AC voltage or DC-intensive modules and as close to the bottom of the SLC enclosure as practical to minimize electrical noise coupling.
