Allen-Bradley 1756-IM16I/A ControlLogix AC Digital Input Module

The Allen-Bradley 1756-IM16I/A, also cataloged as the 1756-IM16I/A isolated digital input module, serves as a ControlLogix backplane I/O interface device for processing 159–265 VAC discrete AC state signals across 16 independently isolated input channels within ControlLogix chassis systems. The Allen-Bradley 1756-IM16I/A (1756-IM16I/A AC digital input module) performs direct AC signal threshold detection and converts field-level voltage states into backplane-accessible digital input data.

Suffix Breakdown & Model Matrix

• 1756: ControlLogix chassis-based I/O platform

• IM16: 16-channel AC digital input structure

• I: Individually isolated input architecture

• /A: Hardware revision identifier

No further functional segmentation is defined in the provided configuration data.

Hardware Specifications

ControlLogix Backplane Bus Deterministic I/O Behavior

The 1756-IM16I/A operates within the ControlLogix backplane communication structure, where input state transitions are synchronized to scheduled I/O scan cycles managed by the controller task execution system. The module maps AC threshold detection events into digital status bits prior to backplane transfer, ensuring consistent state representation across the chassis I/O data table.

Backplane throughput behavior is governed by chassis slot configuration and controller task rate. The module does not perform field protocol conversion; all AC signal interpretation is completed at the input stage prior to deterministic data publishing.

Frequently Asked Questions (FAQ)

Q: Can the input delay time be adjusted per channel?
A: The module supports programmable input filtering with selectable 9 ms or 18 ms delay settings. Configuration is applied at module level and affects all channels uniformly.

Q: What happens if input current falls below 5 mA threshold?
A: Signals below the minimum operating current threshold may not be reliably registered as ON-state transitions, resulting in undefined input recognition behavior.

Q: Is channel-to-channel electrical interaction possible?
A: No. Each channel is individually isolated, preventing electrical coupling or shared reference interaction between adjacent input circuits.

Field Installation Guidelines

• Install module into a compatible 1756 ControlLogix chassis slot with system power removed or per approved insertion procedure

• Fully seat 36-pin RTB or IFM connector prior to energizing field wiring

• Maintain separation between AC input conductors and low-level signal or communication wiring

• Ensure field AC supply remains within 159–265 VAC operating window before commissioning

• Apply proper shielding termination practices for long cable runs to reduce induced noise

• Verify channel configuration and input filtering parameters prior to system startup