Allen-Bradley 1746-IA16/C SLC 500 Digital I/O Module

The Allen-Bradley 1746-IA16/C, also cataloged as the 1746-IA16 AC Input Module, operates as a dedicated hardware component for AC digital signal acquisition within the SLC 500 I/O backplane system.

The module interfaces 85–132 V AC field signals into 16 discrete input channels and converts them into backplane-level digital states for controller scan execution. It is electrically designed for 47–63 Hz input frequency range and supports point-to-point AC sensing with defined inrush and off-state thresholds. Lifecycle status is discontinued as of Nov 24, 2022.

Hardware Specifications

Backplane Bus Communication Characteristics (SLC 500 Architecture)

The module exchanges input state data through the SLC 500 chassis backplane bus with cyclic scan synchronization. Backplane current draw is limited to 5 VDC logic rail consumption, with deterministic update behavior aligned to controller scan time. Channel mapping is fixed per 16-point architecture without field-configurable scaling.

AC Input Signal Conditioning and Threshold Behavior

Input circuitry uses internal impedance conditioning to stabilize 85–132 V AC field signals. OFF-state detection is governed by leakage current discrimination up to 2 mA, preventing false transitions under induced voltage conditions. Inrush tolerance up to 0.8 A supports relay and mechanical contact closure events without input latch distortion.

Frequently Asked Questions (FAQ)

Q: Does the 1746-IA16/C support hot-swap insertion in an energized SLC 500 chassis?
A: The module is not designed for live insertion. Backplane power should be removed before module installation or replacement to avoid bus transient corruption.

Q: What is the backplane current impact during full 16-channel activation?
A: Backplane consumption remains fixed at 0.085 A @ 5 VDC, independent of input channel state transitions.

Q: Is firmware upgrade or field reconfiguration supported?
A: No firmware layer is implemented in this module class. Operation is hardware-defined via backplane mapping only.

Field Installation Guidelines

The module shall be installed in a compatible SLC 500 chassis slot with backplane alignment verified prior to insertion. Terminal wiring must be performed using the removable terminal block with AC input segregation from low-voltage control wiring.

Shielding and grounding practices should ensure single-point earth reference for AC field wiring to minimize induced noise coupling. Conductors must be routed with adequate separation from high-frequency switching lines. Module replacement requires full system power isolation to maintain backplane integrity and prevent signal corruption during insertion or removal.