Allen-Bradley 1794-OF8IH Flex I/O Analog Output Module

Configured for precision process control in distributed I/O architectures, the Allen-Bradley 1794-OF8IH (1794-OF8IH) Flex IO Isolated Analog Output HART Module provides direct physical/electrical execution of eight independent current output channels.

Suffix Breakdown & Model Matrix

• 1794-OF8IH: Base Flex I/O module with 8 isolated analog output channels supporting HART protocol.
• 1794-TB3 / 1794-TB3S: Compatible terminal base options for field wiring termination.

Hardware Specifications

4-20 mA HART Loop Protocol

The 1794-OF8IH supports the HART protocol on all eight isolated output channels, enabling bi-directional communication with intelligent field devices. Each channel provides channel-to-channel isolation, preventing common-mode interference between disparate loops. The module utilizes a 16-bit digital-to-analog converter with a 10 ms conversion rate, ensuring rapid output updates for demanding process applications. Firmware flash compatibility is supported via the Flexbus communication interface, allowing for integrated configuration and maintenance of HART-enabled transmitters or actuators directly through the control system network.

Frequently Asked Questions

Q: Does the 1794-OF8IH support hot-swapping within the Flex I/O backplane?

A: Yes, the module supports removal and insertion under power (RIUP) when mounted on a compatible 1794 terminal base, provided the rack power is active and the system configuration accounts for temporary signal loss.

Q: Is external isolation required between channels?

A: No. The 1794-OF8IH provides galvanic isolation between each of the eight output channels, eliminating the requirement for external signal isolators in most standard loop configurations.

Field Installation Guidelines

1. Ensure the compatible 1794-TB3 or 1794-TB3S terminal base is securely mounted to the DIN-rail.
2. Align the module with the terminal base and rotate into position until the mechanical latch secures the connection to the Flexbus.
3. Terminate field loop wiring to the terminal base, ensuring correct polarity for the 0-20 mA / 4-20 mA output circuits.
4. Route output signal cabling through dedicated shielded conduits or wireways, keeping them separated from high-voltage AC or motor drive power cables to minimize induced noise.
5. Terminate all cable shields to a single, low-impedance earth ground at the cabinet entry to prevent ground loop currents.
6. Verify channel configuration and loop integrity via the PLC programming environment after power-up; ensure the output mode matches the connected field device requirements.