Product Overview

The Allen-Bradley 1797-OB4D is a specialized four-channel digital sourcing output module designed for the FLEX™ Ex I/O system. Engineered specifically for hazardous area applications, this intrinsically safe module allows for the direct control of field devices—such as solenoid valves, small actuators, and motor starters—located in potentially explosive environments. By utilizing a sourcing output architecture, the module simplifies field wiring by referencing all four channels to a single common power supply.

As part of the FLEX Ex family, the 1797-OB4D provides a modular and space-efficient solution that eliminates the need for bulky isolation barriers. It integrates seamlessly into the FLEX I/O backplane, providing high-speed communication and advanced diagnostic capabilities that ensure process safety and maximized uptime in critical industrial sectors like oil and gas, chemical processing, and mining.

Technical Characteristics

• Output Configuration: 4 sourcing digital output channels.

• Architecture: Non-isolated sourcing type with a shared common supply for streamlined wiring.

• Intrinsically Safe Design: Specifically rated for use with FLEX Ex terminal bases in hazardous locations.

• Smart Diagnostics: Individual channel detection for wire-break (open circuit) and short-circuit faults.

• Visual Indicators: Features a dedicated red/green status LED and four yellow channel-state LEDs for immediate on-site troubleshooting.

• Response Performance: High-speed data refresh rate of 2 milliseconds from the system backplane.

• Electronic Protection: Integrated protection circuits prevent module damage during field-side electrical faults.

• Mounting: DIN-rail mountable via compatible FLEX Ex terminal bases (e.g., 1797-TB3 or 1797-TB3S).

• Operating Temperature: Designed for industrial-grade thermal resilience (0°C to 60°C).

• Dimensions: 3.5 x 13 x 14.5 cm.

• Weight: 0.9 kg.

Advanced Fault Detection and Hazardous Area Control

The 1797-OB4D stands out due to its "D" (Diagnostic) designation, which provides granular feedback to the controller. Unlike standard modules, the 1797-OB4D can differentiate between a healthy load and a disconnected wire. When a fault is detected, the status LED provides a flashing red signal, allowing maintenance personnel to pinpoint the failure location without exhaustive manual testing.

This module is optimized for use with ControlLogix® or SLC 500™ systems via a FLEX Ex adapter. Its low-power, intrinsically safe design significantly reduces the thermal footprint within the control enclosure, while the ruggedized housing protects internal electronics from the vibration and humidity common in remote field locations. By providing deterministic control and real-time health monitoring, the 1797-OB4D ensures that critical automated sequences—such as emergency shutdowns or precise dosing—are executed with total reliability.