Allen-Bradley 1771-OFE2 PLC-5 Analog Output Module

Description

The Allen-Bradley 1771-OFE2 (Series A and B) is an intelligent, single-slot analog output module designed for the PLC-5 / 1771 I/O chassis system. It features four (4) individually isolated differential current channels delivering a factory-set 4 to 20 mA output signal. The module converts digital data—supplied via binary, 2's complement binary, or 4-digit binary coded decimal (BCD)—into proportional analog output signals. It can automatically convert raw process values into standard engineering units such as degrees Celsius, degrees Fahrenheit, gallons per minute, or pounds per square inch.

The 1771-OFE2 is widely used to control Final Control Elements (FCE) like Variable Frequency Drives (VFDs), dampers, louvers, and control valves. It is also ideal for executing PID controller outputs in closed loops or retransmitting process variables to signal isolators, panel meters, chart recorders, and data loggers. Powered directly from the I/O backplane, it requires no external power supply and supports block transfer programming (BTW/BTR) for configuration and diagnostic reporting.

Features

• 4 Isolated Channels: Features 4 individually isolated differential current outputs (1000V DC / 1500V optoelectronic isolation).
• Current Output Range: Factory-set 4 to 20 mA DC range.
• Flexible Data Formats: Supports 12-bit natural binary, BCD, or 2's complement binary, with scaling up to ±9999.
• On-Board Engineering Units: Converts raw data directly into units like °C, °F, GPM, or PSI.
• Backplane Powered: Operates solely on 1.5A @ 5V DC chassis backplane power; no external supply needed.
• Fast Response: DAC settling time is a maximum of 0.8 ms, with fast channel scan update times.
• Fail-Safe Modes: Configurable Last State output mode (MAX, MIN, MID, or HOLD LAST STATE) on communication failure.
• Diagnostic LEDs: Front-panel green RUN and red FAULT LEDs with built-in startup self-diagnostics.

Applications

• Driving variable frequency motor speed controllers (VFDs)
• Position control for valves, dampers, and louvers
• Automated PID control loop output execution
• Signal retransmission to panel meters, chart recorders, and data loggers

Technical Specifications

Field Wiring Arm Connections (1771-WC)

The 1771-WC wiring arm allows the module to be swapped without disconnecting the field wiring.

Installation Guidelines

• Power Precaution: Always disconnect and lock out backplane and field wiring power before inserting, removing, or wiring the module.
• Backplane Keying: Install backplane keying bands between pins 10 and 12, and between pins 26 and 28 on the upper connector to ensure correct module orientation.
• Chassis Location: The module can be installed in any single slot of a 1771 I/O chassis. Avoid placing it in the same module group as discrete high-density modules or directly adjacent to AC or high-voltage DC modules.
• Wiring and Shielding: Use Belden 8761 shielded single-pair cable for signal lines. Extend the foil shield and drain wire to the chassis end only and connect to a single-point ground bus.
• Field Wiring Arm: Attach the 1771-WC wiring arm to the chassis horizontal bar. Tighten terminal screws to a torque of 7-9 lb-in (0.6-1.1 Nm).

Compliance and Certifications

• CSA certified (Class I, Division 2, Groups A, B, C, D hazardous or non-hazardous locations)
• UL listed (Class I, Division 2, Groups A, B, C, D hazardous or non-hazardous locations)
• CE marked (EMC Directive 89/336/EEC per EN 50081-2 & EN 50082-2; Low Voltage Directive 73/23/EEC per EN 61131-2)