1756-OF8IH I/O Modules Allen-Bradley

Allen-Bradley 1756-OF8IH Isolated HART Analog Output Module

Core Technical Specifications

• Brand & Manufacturer: Allen Bradley
• Series: ControlLogix
• Model Number: 1756-OF8IH
• Module Type: Isolated HART Analog Output Module
• Channels: 8 Isolated Differential Outputs
• HART Capability: 1 dedicated modem per channel (HART 5, 6, 7)
• Output Signal Range: 0-20 mA and 4-20 mA
• Resolution: 15 bits across 24 mA
• Data Format: IEEE 32-bit floating point

Electrical & Isolation Characteristics

• Isolation Rating (Output-to-Backplane): 250V reinforced insulation (tested at 3535V DC).
• Isolation Rating (Output-to-Output/Ground): 250V basic insulation (tested at 2120V DC).
• Overvoltage Protection: +/- 24 Volts DC.
• Short-Circuit Protection: Electronically limits output current to ≤ 21 mA.
• Drive Capability: 50-750 Ω load (with short-circuit survival).
• Load Reactance: 10 μH maximum.
• Backplane Current Draw: ~400 mA at 24V DC.

Performance & Timing

• Settling Time: < 100 ms (HART enabled), < 23 ms (HART disabled).
• HART Scan Time: Estimated 1 second per module with HART enabled.
• Calibration Accuracy: 0.15% at 4-20 mA range.
• Module Error: 0.3% at 4-20 mA.
• Calibration Interval: Standard recommendation is 12 months.
• Drift: ±3 ppm (Offset), ±4 ppm (Gain).

Environmental & Operational Data

• Operating Temperature: 0°C to 60°C (32°F to 140°F).
• Humidity: 5-95% non-condensing.
• Temperature Code: T4A (North America), T4 (ATEX/IEC).
• Enclosure Type: Open-style (requires a ControlLogix chassis).
• Output Conversion Method: R-Ladder DAC.

Frequently Asked Questions (FAQ)

• Q: What is the key feature of the 1756-OF8IH compared to standard analog modules?
  A: The 1756-OF8IH provides individual isolation for each of its 8 output channels, preventing noise and fault propagation between loops.
• Q: What HART versions does this module support?
  A: It supports HART 5, 6, and 7 protocols with full read/write capability for each channel.
• Q: What kind of protection does the module offer for field wiring faults?
  A: It features overvoltage protection (±24V) and electronic short-circuit protection that limits output current.
• Q: What is the settling time for output changes?
  A: With HART disabled, settling time is under 23 ms. With HART enabled on the channel, it is under 100 ms.
• Q: Do you stock the 1756-OF8IH for immediate shipment?
  A: Yes, the 1756-OF8IH is typically available from our stock for fast delivery.