Allen-Bradley 1746-NO8I SLC 500 Analog Output Module

The Allen-Bradley 1746-NO8I, also cataloged as the 1746-NO8I Analog Output Module, operates as a dedicated hardware component for 0-20 mA signal generation within SLC 500 backplane-based control architectures. Configured for multi-channel analog current synthesis, the Allen-Bradley 1746-NO8I provides direct electrical output control across 8 channels with 16-bit conversion resolution through SLC 500 rack integration.

Suffix Breakdown & Model Matrix

The 1746-NO8I designation follows SLC 500 module structuring:

• 1746: SLC 500 I/O platform identifier

• NO8: 8-channel analog output configuration

• I: Current output variant (0-20 mA class)
  No further functional segmentation or option coding is defined.

Hardware Specifications

Backplane Bus Timing and Analog Output Refresh Behavior

Within the SLC 500 architecture, the 1746-NO8I executes analog signal updates via cyclic backplane scan execution. Each channel output is refreshed at approximately 2 ms intervals, with deterministic synchronization to SLC processor scan cycles. Backplane current loading (5 V and 24 V domains) defines module density limits within the rack, while DAC conversion maintains 16-bit resolution mapping for current loop generation.

Frequently Asked Questions (FAQ)

Q: Does the 1746-NO8I support hot insertion into an energized SLC rack?
A: No. The module is not designed for live insertion. Power must be removed from the rack before installation or removal to avoid backplane damage.

Q: Are all 8 analog outputs electrically isolated per channel?
A: No. The outputs share a common reference structure with limited system-level isolation (50 V continuous), not per-channel isolation.

Q: What happens when backplane current limits are exceeded?
A: Exceeding 5 V or 24 V backplane current limits can cause module initialization failure or unstable DAC output behavior during scan cycles.

Field Installation Guidelines

Insert the module into the SLC 500 rack until fully seated in the backplane connector to ensure stable signal and power distribution. Maintain correct wire gauge selection (22–14 AWG) for analog current loop integrity. Keep analog wiring separated from high-voltage switching conductors to reduce induced noise into 0-20 mA loops. Shield grounding shall be implemented at a single reference point to avoid loop current distortion. Ensure rack power is removed before insertion or extraction to prevent backplane transients.