Allen-Bradley 1756-IF16IHK ControlLogix HART Interface Module

The Allen-Bradley 1756-IF16IHK, also cataloged as the 1756-IF16IHK HART Interface Module, operates as a dedicated hardware component for acquisition and digitization of 0-20 mA and 4-20 mA analog signals within ControlLogix backplane I/O architectures. The module integrates 16 independent HART-enabled input channels with per-channel modem architecture.

Hardware Specifications

ControlLogix Backplane Communication and HART Integration

The module operates within the ControlLogix backplane via deterministic I/O scheduling, where analog sampling and HART superimposed digital communication are multiplexed per channel. Each input channel contains an independent HART modem enabling simultaneous analog loop measurement and digital field device interrogation without shared channel arbitration.

Backplane current draw scaling is fixed at 225 mA on 5.1 VDC rail, with additional 24 VDC domain consumption reaching 200 mA under full channel activation. I/O scan timing is governed by chassis controller task configuration and is not fixed at module level.

Channel-to-channel electrical separation is maintained through isolation barriers rated at 250 V continuous, preventing loop cross-coupling during mixed 4-20 mA and HART overlay operation.

Frequently Asked Questions

Q: Can the module support hot insertion in an energized ControlLogix chassis?
A: The module is designed for ControlLogix backplane hot-swap operation, but field wiring integrity at the RTB must be maintained during insertion to avoid transient loop interruption.

Q: Does each channel maintain independent HART communication paths?
A: Yes, each of the 16 channels includes a dedicated HART modem, enabling parallel digital communication without shared bus contention.

Q: What limits the high-speed acquisition mode behavior?
A: High-speed operation is constrained by internal multiplexing, reducing active simultaneous channels while maintaining fixed backplane update scheduling.

Field Installation Guidelines

Backplane insertion must follow chassis power-down verification or approved hot-swap procedure depending on system configuration. Terminal blocks (RTB or IFM) must be fully seated prior to loop energization.

Shielded analog signal cables should be grounded at a single chassis reference point to prevent ground loop currents affecting 250 ohm input impedance stability. Wiring separation between 4-20 mA loops and high-voltage conductors is required to maintain isolation integrity.

Torque and engagement of removable terminal blocks should follow ControlLogix chassis mechanical locking limits without over-stressing connector pins.