1756-OF8IH HART Analog Output Module | Allen Bradley

Configured for high-precision process signal control in ControlLogix platforms, the Allen Bradley 1756-OF8IH (1756-OF8IH HART Analog Output Module) provides direct physical and electrical execution of 8 isolated current output channels supporting the HART communication protocol.

Hardware Specifications

Profinet / EtherNet/IP Deterministic Networks

The 1756-OF8IH leverages ControlLogix backplane bus communication velocity to ensure deterministic output updates. The module architecture facilitates I/O density scaling by supporting 8 HART-enabled channels within a single chassis slot. Deterministic performance is maintained through strict timing controls on the R-Ladder DAC conversion cycle, ensuring that field process variables and HART diagnostic data are synchronized with the controller scan. Firmware flash compatibility is mandatory to support the host controller's specific HART communication stack versions, ensuring consistent integration into EtherNet/IP or ControlNet architectures.

Frequently Asked Questions

Q: Does this module support hot-swapping?

A: Yes. The 1756-OF8IH supports Removal and Insertion Under Power (RIUP). However, operators must confirm that the field process is in a safe state prior to module removal, as the output channels will transition to pre-configured fault states upon extraction.

Q: How is the output isolation managed?

A: The module provides 250 V continuous isolation to protect the backplane and adjacent modules from field-side electrical faults or common-mode noise. Ensure the field wiring is properly shielded to maintain this isolation integrity.

Field Installation Guidelines

1. Mounting: Seat the module into the ControlLogix chassis and lock the housing levers. Ensure the module is fully aligned with the backplane connector before applying power.
2. Field Wiring: Use shielded twisted-pair cables for current loop connections. Terminate the shields at the chassis ground or the designated grounding bar to suppress EMI/RFI.
3. Load Management: Verify that the connected load reactance does not exceed 10 µH. Exceeding this limit may cause instability in the current loop regulation.
4. Configuration: Utilize the integrated configuration software to define output ranges and HART protocol parameters. Verify that the current loop is continuous before final commissioning to avoid open-circuit fault reporting.
5. Environment: Ensure the installation area maintains a non-condensing relative humidity between 5% and 95% and stays within the 0 to 60 deg C operating temperature range.