Allen-Bradley 1771-IFF Analog Input Module for PLC-5 Systems

Product Overview

When you need reliable analog signal acquisition in a PLC-5 system, the Allen-Bradley 1771-IFF analog input module delivers precise data conversion and flexible configuration. This module uses block transfer programming to interface a variety of analog input devices—such as temperature sensors, pressure transmitters, and flow meters—with the PLC processor. It supports either 8 differential selectable inputs or 16 single-ended inputs, giving you the flexibility to match your field wiring requirements. The 1771-IFF does not require an external power supply, simplifying installation and reducing wiring complexity.

Key Technical Specifications

The 1771-IFF offers selectable input ranges to accommodate different signal types:

Voltage Ranges: 0-5 V dc, 1-5 V dc, +/- 5 V dc, +/- 10 V dc

Current Ranges: 4-20 mA, 0-20 mA, +/- 20 mA

Input Configuration: 8 differential or 16 single-ended, selectable

Data Format: Natural Binary or BCD scaling to +/- 9999

Channel Update Time: 5 ms for 8 channels; 10 ms for 16 channels

Resolution: 12 bits plus sign

Backplane Current: 750 mA

External Power Required: No

Wiring Arm: 1771-WG

Coating: Conformal coat

These specifications make the 1771-IFF suitable for both voltage and current loop signals commonly found in industrial process control.

Industry Applications

The 1771-IFF excels in applications that require accurate analog measurement. In temperature sensing, you can connect thermocouples or RTD transmitters with 4-20 mA output and scale the data using BCD format. For pressure monitoring in hydraulic systems, the differential input mode rejects common-mode noise, improving signal integrity. Flow metering applications benefit from the fast 5 ms update time when using 8 channels, enabling real-time flow rate calculations. The module's conformal coating protects against moisture and contaminants in harsh industrial environments.

Installation and Setup Guidance

Mount the 1771-IFF in any single slot of a PLC-5 I/O chassis. Use the 1771-WG wiring arm to connect field wiring; this arm allows module replacement without disconnecting wires. For correct keying, install keying bands between pins 10 and 12 on the lower connector and between pins 24 and 26 on the upper connector. The front panel includes a green RUN indicator and a red FAULT indicator for quick status checks. No external power supply is needed—the module draws 750 mA from the backplane.

Comparison with Similar Modules

Compared to other PLC-5 analog input modules, the 1771-IFF offers a unique combination of differential and single-ended input flexibility. For example:

1771-IFE: 8 differential inputs only, no single-ended option

1771-IF: 4 differential inputs, lower channel count

1771-IFF: 8 differential or 16 single-ended, higher density and flexibility

This makes the 1771-IFF ideal for applications where you need to mix signal types or maximize input count in a single slot.

Maintenance and Reliability

The 1771-IFF includes input filtering to reduce electrical noise and optoelectrical isolation to protect system circuits from transients. Periodic inspection of the wiring arm connections and front panel indicators is recommended. The conformal coating enhances resistance to humidity and dust. For predictable fault response, the module can be configured to default to user-defined values if input communication is disrupted.

Selection Guide and Purchasing Advice

Before purchasing the 1771-IFF, verify your PLC-5 chassis compatibility and available slot space. Ensure you have the 1771-WG wiring arm for easy installation. For complete technical specifications and current availability, contact BluePLC Industrial. We stock genuine Allen-Bradley modules and can assist with replacement or upgrade needs.