Allen-Bradley 1756-IF8IH – HART Isolated Analog Input Module

Overview

The 1756-IF8IH is an 8-channel HART Analog I/O Module designed for the Allen-Bradley ControlLogix system. Each channel is equipped with a HART modem, allowing communication with HART devices using revisions 5, 6, or 7. This module requires a removable terminal block (RTB), either 1756-TBCH or 1756-TBS6H, for installation.

The 1756-IF8IH provides two selectable input ranges (0–20 mA or 4–20 mA), with the 4–20 mA range used for HART instruments. Users can select from four data formats: analog only, analog + HART PV, analog + HART by channel without Configure HART Device, and analog + HART by channel with Configure HART Device.

This module features high-resolution signal acquisition (16–21 bits) and robust detection capabilities, including overrange, underrange, and open-circuit detection.

Technical Specifications

General Information

• Manufacturer: Rockwell Automation

• Brand: Allen-Bradley

• Part Number/Catalog No.: 1756-IF8IH

• Series: ControlLogix

• Module Type: HART Isolated Analog Input Module

• Number of Channels: 8 Isolated Differential

• Enclosure Type: Open

• Overvoltage Protection: ±24 V

Input Specifications

• Input Range: 0–20 mA or 4–20 mA

• Resolution: 16–21 bits

• HART Communication: 1 device per channel, supports HART revisions 5, 6, 7

• Data Formats:

• Analog only

• Analog + HART PV

• Analog + HART by channel (Configure HART device: No)

• Analog + HART by channel (Configure HART device: Yes)

Detection Features

• Overrange / Underrange Detection – Alerts when inputs exceed module limits

• Open-Circuit Detection:

• 4–20 mA range: reports negative full-scale value within 5 seconds

• 0–20 mA range: reports 0 mA for open-circuit condition

Filtering and Sampling

• Each channel includes an ADC filter for noise attenuation at 50/60 Hz

• Digital filters reduce input signal transients

• Real-time sampling instructs module to scan channels and broadcast data to the local chassis backplane

The 1756-IF8IH is an ideal solution for ControlLogix applications requiring precise analog input measurement, HART communication, and advanced detection features, ensuring reliable operation in industrial environments.