Allen-Bradley 1756-IF16IH ControlLogix HART Analog Input Module

The Allen-Bradley 1756-IF16IH, also cataloged as the 1756-IF16IH HART analog input module, operates as a dedicated hardware component for acquisition of 0-20 mA and 4-20 mA process signals with per-channel HART modulation within ControlLogix backplane architectures. The module executes 16-channel isolated analog conversion with independent HART modem coupling on each input path.

Hardware Specifications

ControlLogix Backplane Execution and HART Channel Architecture

The module implements per-channel HART modem integration, where each analog input channel maintains independent digital overlay communication over the same 4-20 mA loop. The ControlLogix backplane schedules analog sampling and HART transaction cycles as separate execution domains, allowing simultaneous signal conversion and field device diagnostics.

Galvanic isolation is implemented across channel-to-channel, channel-to-backplane, and channel-to-frame ground domains at a continuous 250 V AC rms level. This structure prevents loop interference between HART communication carriers and analog measurement circuits under shared chassis conditions.

Input impedance is fixed at 250 ohms (+/- 5 ohms), defining loop current-to-voltage conversion behavior for transmitter interface compatibility.

Frequently Asked Questions (FAQ)

Q: Can each input channel execute HART communication independently?
A: Yes. Each of the 16 channels includes a dedicated HART modem, allowing parallel field device communication without shared multiplexing.

Q: What is the effect of backplane current draw during full channel operation?
A: Backplane loading remains at 225 mA at 5.1 VDC under nominal operation; inrush current peaks occur only during module energization.

Q: Does the module support channel-to-channel electrical isolation?
A: Yes. Channel-to-channel, channel-to-backplane, and channel-to-frame isolation are implemented with 250 V AC rms continuous rating.

Field Installation Guidelines

Insert the module into a compatible ControlLogix chassis slot with system power removed. Ensure proper seating of the terminal assembly prior to energization.

Maintain separation between HART/analog loop wiring and backplane power conductors to reduce capacitive coupling into high-resolution conversion stages. Shield termination should be implemented at a single-point ground reference within the control cabinet to avoid loop-induced offset errors in 4-20 mA circuits.

Terminal impedance (250 ohm network path) must remain stable across all channels to preserve HART carrier modulation integrity.