Allen-Bradley 1756-OF8 ControlLogix Analog Output Module

The Allen-Bradley 1756-OF8, also cataloged as the 1756-OF8 Analog Output Module, operates as a dedicated hardware component for 8-channel analog current and voltage signal generation within ControlLogix chassis assemblies.

Hardware Specifications

Deterministic Backplane & I/O Density Scaling

The module receives digital register values across the ControlLogix system backplane bus, executing 15-bit signed digital-to-analog conversion for real-time channel sampling. Internal firmware scaling translates raw binary data directly into engineering units, while onboard data alarming evaluates threshold limits independent of main controller scan cycles. Backplane bus communication velocity allows rapid EtherNet/IP and ControlNet synchronization across all 8 output channels, preventing signal drift or processing latencies during dense I/O system operations.

Frequently Asked Questions

Q: How is physical wire routing misconnection prevented during module replacement?

A: The module supports software-configurable electronic module keying alongside user-defined mechanical keying tabs on the 20-pin Removable Terminal Block (RTB).

Q: What dynamic resolution does the internal digital-to-analog converter deliver for field signals?

A: The converter provides a 15-bit signed analog resolution across both the -10 V to +10 VDC and 0 mA to 20 mA operating ranges.

Q: Can onboard data alarming function independently of controller execution logic?

A: Yes, onboard data alarming performs real-time limit validation directly within module memory to identify out-of-spec signals without increasing CPU scan overhead.

Field Installation Guidelines

Turn off chassis power or follow designated Removal and Insertion Under Power (RIUP) safety procedures before inserting the module into an open ControlLogix slot. Align the circuit board with the chassis guides and press firmly until both latching mechanisms snap into place.

Connect field wiring using the designated 20-pin RTB assembly. Configure mechanical RTB keying tabs to prevent accidental insertion into incompatible module types. Use shielded twisted-pair cables for signal output wiring, landing the cable shields at a central enclosure earth ground bar. Maintain distinct separation between low-voltage analog output cabling and high-voltage AC power conductors within panel wireways to minimize noise coupling.