Allen-Bradley 1756-OB16D ControlLogix 16-Point Diagnostic Digital Output Module

Product Overview

The 1756-OB16D operates as an intelligent 16-point diagnostic digital output module for the Allen-Bradley ControlLogix system. This module provides 24V DC sourcing outputs with advanced onboard monitoring capabilities, allowing the controller to detect field-side faults such as short circuits, no-load conditions, and output verification failures. We supply this unit as 100% Brand New original stock, ensuring your automation architecture maintains maximum fault visibility and operational safety.

Technical Specifications

The 1756-OB16D utilizes high-precision diagnostics and robust electrical ratings for industrial control:

• Outputs: 16 Diagnostic Sourcing Outputs (8 points per group)

• Voltage Category: 24V DC Source

• Operating Voltage Range: 19.2 to 30V DC

• Backplane Current Draw: 250 mA @ 5.1V DC / 140 mA @ 24V DC

• Total Backplane Power: 4.64 W

• Thermal Dissipation: 11.25 BTU/hr

• Short Trip Protection: 8 A for 180 ms (min) / 10 A for 120 ms (min)

• Diagnostic Timestamp Accuracy: ±1 ms

• Isolation Voltage: 250V continuous (Basic insulation between outputs and backplane)

• Scheduled Outputs: Synchronization within 16.7 s max via Coordinated System Time (CST)

• Shipping Weight: 2 kg

Engineering Advantages

• Predictive Fault Detection: The 1756-OB16D monitors both On-state and Off-state conditions. It identifies an "Open Load" when the output is Off and verifies the load presence when the output is On. This proactive monitoring allows maintenance teams to replace failing actuators before a complete process shutdown occurs.

• Precision Diagnostic Timestamping: The module assigns a ±1 ms timestamp to every diagnostic event. This accuracy allows engineers to perform high-resolution sequence-of-events (SOE) analysis, helping to pinpoint the exact root cause of intermittent electrical faults in high-speed machinery.

• Configurable Pulse Testing: The hardware executes sub-millisecond pulse tests to verify output circuit integrity without actually energizing the load. You can configure the maximum pulse width to ensure compatibility with sensitive field devices, preventing accidental triggering while maintaining safety coverage.

• High-Current Surge Handling: The integrated "Short Trip" logic manages high inrush currents typical of large solenoid valves or DC contactors. It allows up to 10 A for 120 ms, preventing nuisance tripping during the initial energization phase while still providing rapid short-circuit protection for the wiring.

FAQs

• Is the 1756-OB16D provided as a brand new original unit?

  Yes. We supply this module strictly as 100% Brand New original factory equipment. It arrives in the original Allen-Bradley packaging with all factory seals intact to ensure 100% diagnostic reliability.

• Can the 1756-OB16D detect a blown fuse in the field?

  Yes. By utilizing the "Output Verification" and "No Load" diagnostic features, the module identifies if power fails to reach the load. If a field-side fuse blows, the module immediately reports a diagnostic fault to the controller and triggers the corresponding status LED.

• Does this module require a specific Removable Terminal Block (RTB)?

  The 1756-OB16D requires a 36-pin RTB due to the wiring density of the diagnostic groups. We recommend the 1756-TBCH (Cage Clamp) or 1756-TBSH (Spring Clamp) for secure industrial terminations.

• How does "Scheduled Output" synchronization benefit my application?

  This feature synchronizes all outputs within 16.7 seconds relative to the Coordinated System Time (CST). This is critical for applications requiring precise multi-axis coordination or time-stamped control actions across multiple chassis in a distributed ControlLogix network.