Overview
The Allen-Bradley 1771-OFE2 is a classic analog output module from the 1771 product family, designed for PLC-5 and Universal I/O chassis-based automation systems. This module features four isolated differential analog output channels that deliver 4-20 mA current signals—a live-zero standard for reliable process control. The 1771-OFE2 converts digital values (binary or BCD format) into proportional current outputs, making it essential for modulating equipment such as variable frequency drives (VFDs), control valves, dampers, louvers, and proportional solenoids.
Key Features
- Four isolated analog output channels—each independently isolated for noise immunity
- 4-20 mA output range—industry-standard current loop with live-zero
- 12-bit digital resolution—accurate conversion across the full output span
- Binary and BCD scaling—supports ±9999 data format for flexible engineering unit mapping
- Intelligent block transfer architecture—programmable in RSLogix/Studio 5000 via block transfer instructions
- Includes 1771-WC wiring arm—simplifies field wiring and module replacement without terminal disconnection
- Test mode configuration—selectable output level (zero, mid-scale, full-scale) during reset conditions
- Status indicators—green RUN and red FAULT LEDs for quick diagnostics
Technical Specifications
- Output Channels: 4 (isolated differential)
- Output Current Range: 4–20 mA
- Digital Resolution: 12-bit binary
- Load Resistance (Max): 1200 Ω per channel
- Backplane Current Consumption: 1.4 A @ 5 VDC
- Channel Update Time (BCD): 8 ms per 4 channels
- Channel Update Time (Binary): 1.6 ms per 4 channels
- Power Dissipation: 7.9 W (maximum)
- Thermal Dissipation: 26.9 BTU/hr
- Isolation (Optoelectronic): 1500 VDC
- Surge Isolation: 850 V for 1 second
- Mounting: Single slot, any 1771 I/O chassis (except leftmost Remote I/O slot)
- Field Wiring Arm: Cat. 1771-WC
- Keying Positions: Pins 10–12 and 26–28 (standard OFE configuration)
- Weight: 1.26 lbs
- Product Status: Discontinued by Rockwell Automation (March 2021)
Typical Applications
- HVAC control—proportional damper and valve actuation
- Process control—transmitting PID controller outputs to final control elements
- Motor drive control—speed modulation via 4-20 mA analog input to Variable Frequency Drives
- Instrumentation—feeding signals to analog panel meters, data loggers, and signal isolators
- Legacy PLC-5 system upgrades—maintaining existing installation compatibility
Compatibility & Replacements
Compatible With
- Allen-Bradley PLC-5 systems (and remote I/O configurations)
- Allen-Bradley Universal I/O Chassis: 1771-A1B, 1771-A2B, 1771-A3B, 1771-A4B
- Block Transfer-based RSLogix 5 programming
- Any 1771-series I/O chassis environment
Replaces / Drop-In Replacement For
- Original 1771-OFE2 modules (all revisions)
- Functionally equivalent to earlier 1771-OFE2 production runs
- Note: Not compatible with 1771-OFE1 (voltage output) applications or 0–20 mA systems without reconfiguration
Works With
- RSLogix 5 / Studio 5000—programming via Block Transfer instructions
- 4-20 mA devices—proportional valve controllers, damper motors, solenoid drivers
- Analog instruments—panel meters, chart recorders, signal isolators, data loggers
- Shielded twisted-pair cabling—recommended maximum length 50 ft for noise immunity
