The Allen-Bradley 1771-OFE2, also cataloged as the 1771-OFE2 Analog Output Module, operates as a dedicated hardware component for 4-20 mA current loop signal generation within PLC-5 I/O chassis platforms.
Suffix Breakdown & Model Matrix
Base Model
Module Type
Output Channels
Output Signal Range
Isolation Rating
1771-OFE2
Analog Output Module
4 isolated channels
4-20 mA
1000 V differential / 850 VDC
Hardware Specifications
Parameter
Specification
Model
1771-OFE2
Brand
Allen-Bradley
Origin
USA / Global Manufacturing standard
Weight
1.88 lbs (0.85 kg)
Dimensions
Single-slot 1771 I/O chassis module form factor
Operating Temp
0 to 60 deg C (32 to 140 deg F)
Power Consumption
Power dissipation: 7.9 W (Thermal: 26.9 BTU/hr)
Output Channels
4 individually isolated differential outputs
Output Signal Range
4-20 mA
Digital Resolution
12-bit binary
Data Format
Natural Binary or BCD Scaling (+/- 9999)
Backplane Current
1.50 A at 5 VDC (No external power required)
Field Wiring Arm
1771-WC or 1771-WH
Keying Position
Between 10 and 12; Between 26 and 28
PLC-5 I/O Density Scaling & Backplane Bus Integration
The 1771-OFE2 interfaces directly with the 1771 I/O backplane bus to deliver high-density analog output control without requiring external field power supplies. Incorporating 1500 V optoelectrical isolation and 1000 V channel-to-channel differential protection, the module prevents ground loops and electrical transient propagation from affecting backplane bus communication velocity. The onboard Digital-to-Analog Converter (DAC) updates all 4 channels in 1.6 ms (Natural Binary) or 8 ms (BCD), supporting continuous output synchronization for process loops.
Frequently Asked Questions
Q: Does the 1771-OFE2 require an external power supply to drive the 4-20 mA loop outputs?
A: No, the module draws all required operational power (1.50 A at 5 VDC) directly from the 1771 chassis backplane bus.
Q: What diagnostic LED indicators are provided on the front panel of the 1771-OFE2?
A: The module features 2 LED indicators: a green power status LED and a red fault indicator LED that illuminates if start-up self-checks detect a module error.
Field Installation Guidelines
Ensure the 1771 I/O chassis backplane power is disconnected before installing or removing the module.
Insert plastic keying bands into the chassis backplane connector between pins 10-12 and 26-28 to ensure proper slot keying.
Align the module circuit board with the chassis slot card guides and slide it firmly into place until fully seated.
Install the 1771-WC wiring arm and terminate field conductors using 12 AWG stranded or solid shielded cable (Belden 8761 recommended).
Tighten wiring arm terminal screws to a torque rating of 7-9 in-lbs (0.8-1.0 N-m).
