Allen-Bradley 1756-OB16I ControlLogix Isolated DC Output Module

1756-OB16I: An Isolated DC Output Module for ControlLogix

The 1756-OB16I is a 16-channel isolated DC output module for the ControlLogix platform, and the isolation is the distinguishing feature. Each output channel is isolated from the backplane, which means field circuits cannot propagate a fault between channels or back into the rack.

Where outputs drive relays, solenoids and lamps across multiple supplies, that isolation is what removes an entire class of fault. A shared-return output module on a machine with mixed supplies will eventually be brought down by a fault on one field circuit that has no independent return path.

ControlLogix Output Modules

Output modules in this family differ in channel count, isolation and output type. The three determine whether a module fits both the rack and the field wiring:

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What Isolation Changes in the Field

With per-channel isolation, a field circuit fault stays on that channel. The failure mode becomes a single output dropping out rather than a group of outputs going down together, and — more importantly — the fault no longer propagates to other channels or into the rack.

On machines with inductive loads, per-channel isolation also removes the shared-return path where a switching transient from one circuit can appear across another. That matters most where a relay or solenoid shares a supply rail with measurement or control circuits that should stay clean.

Field Wiring and Load Types

Confirm the output voltage and current rating against the actual loads on each channel. Where a channel drives a relay coil rather than the load directly, the coil is the load the module has to switch — and inductive switching imposes its own derating and lifetime implications that a resistive load does not.

Flyback suppression across inductive loads extends contact and transistor life in a way that is cheap to add at commissioning and expensive to retrofit later.

Commissioning by Channel

With 16 isolated channels, bring the outputs up in groups and verify each point individually against its field device. Per-channel isolation means a group can appear healthy while individual channels have failed — the module will not report a group fault that would be visible on a shared-return module.

Supply & terms: Stock status: In Stock · Condition: New · Warranty: One Year · Origin: US. Listed by AutoDCS Tech Parts Team · Last updated 2026-10-07.

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