1756-OF8 Allen-Bradley ControlLogix Analog Output Module New

Overview

The 1756-OF8 operates as an 8-channel analog current and voltage output module designed for the Allen-Bradley ControlLogix architecture. Built by Rockwell Automation, this high-resolution module delivers precise signal modulation for variable speed drives, control valves, and field instrumentation in demanding industrial automation setups.

Every channel on the 1756-OF8 module provides software-configurable signal ranges spanning +/-10V DC or 0-20 mA. Operating across a 15-bit resolution spectrum, it processes dynamic control loops with scan speeds down to 8 ms in integer mode and 12 ms in floating-point mode.

Engineering Specifications

The table below organizes critical electrical, timing, and mechanical performance metrics using MECE classification principles for direct technical comparison.

• Brand: Allen-Bradley / Rockwell Automation
• Catalog Number: 1756-OF8
• Product Series: ControlLogix System
• Module Type: Analog Output Module
• Output Channels: 8 individual points (Current or Voltage configurable)
• Output Voltage Range: +/-10V DC
• Output Current Range: 0 to 20 mA
• Digital Signal Resolution: 15-bit across 10.4V (320 µV/bit) and 21 mA (650 nA/bit)
• Module Scan Time: 8 ms (Integer mode) / 12 ms (32-bit Floating Point mode)
• Overall Module Error: 0.15% full scale (Voltage) / 0.30% full scale (Current)
• DAC Conversion Method: R-Ladder DAC with monotonicity and no missing codes
• Backplane Current Draw: 140 mA at 5V DC / 210 mA at 24V DC
• Maximum Power Dissipation: 4.9 Watts at 60 °C
• Circuit Protection: Current limited to 21 mA or less; short circuit and 24V DC overvoltage protection
• Isolation Voltage: 250V continuous reinforced isolation (tested at 1350V AC for 2 seconds channel-to-backplane)
• Thermal Drift Rate: Offset drift 50 ppm/°C; Gain drift 25 ppm/°C (voltage) / 50 ppm/°C (current)
• Compatible Wiring Block: 1756-TBNH (18-pin spring) or 1756-TBSH (20-pin cage clamp)
• Wire Conductor Size: 0.33 to 2.1 mm² (22 to 14 AWG) copper rated at 105 °C minimum
• Operating Environmental Limits: Temperature 0 to 60 °C (32 to 140 °F); Shock 30G; Vibration 2G at 10-500 Hz
• Temperature Hazardous Ratings: Class I Div 2 Groups A,B,C,D (T4A North America, T4 ATEX/IEC)
• Global Product Identifiers: UPC 10612598171894 and UNSPSC 32151705

Wiring & Mechanical Installation Procedures

Executing proper mechanical and electrical installation prevents ground loops and signal interference on industrial field wiring.

• De-energize the ControlLogix chassis backplane power supply prior to module insertion or extraction.
• Align the 1756-OF8 printed circuit board with top and bottom chassis guides in any available slot.
• Slide the module inward until side locking tabs engage cleanly with the backplane connector.
• Select shielded twisted-pair cabling when wiring 0-20 mA current loops to minimize EMI coupling.
• Terminate wiring using either the 1756-TBNH or 1756-TBSH removable terminal block assembly.
• Torque terminal block screws to manufacturer specification and snap the protective front door closed.

Hardware Diagnostics & Protection Systems

The 1756-OF8 incorporates built-in hardware protection to safeguard internal output drivers and connected equipment during field faults.

Integrated electronic current limiters restrict maximum current output to 21 mA or less during short-circuit conditions. Open-circuit detection monitors field loops when configured in current output mode, while overvoltage clamping handles back-fed surges up to 24V DC without damaging internal electronics.

Target Equipment & Field Applications

Control engineers specify the 1756-OF8 inside automated processing environments where exact command signals drive final control elements.

It directly interfaces with variable frequency drives (VFDs) for speed reference modulation, modulating control valves in fluid management, proportional servo amplifiers, and chart recorders. Typical industries include petrochemical refining, paper conversion, power generation, and continuous metals processing.

Global PLC Spare HUB's Insight & Field Experience

Our control systems division evaluates hundreds of industrial I/O modules operating under severe plant conditions. The 1756-OF8 exhibits exceptional backplane isolation, shielding sensitive logic processors from high-voltage transients induced on field wiring cables.

In a continuous chemical batching process, an engineering team experienced intermittent zero-point drift on analog valve positioning. Troubleshooting revealed high common-mode noise generated by adjacent high-horsepower VFD motor leads. Swapping to the 1756-TBSH shielded terminal block and landing cable shields exclusively at the cabinet single-point ground eliminated noise induction. We strongly advise utilizing shielded twisted-pair conductors with single-point grounding when driving voltage references over 50 feet.

System Selection & Integration Guidance

Verifying module requirements prior to ordering ensures seamless software setup inside Studio 5000 or RSLogix 5000 programming tools.

Choose the 1756-OF8 when 8 standard non-isolated analog output channels satisfy system requirements. If your process requires channel-to-channel isolation to prevent loop interference without external isolators, evaluate the 1756-OF8I isolated variant instead. Always calculate total backplane current draw against power supply capacity when adding expansion I/O to existing chassis layouts.

Shipping Terms & 12-Month Warranty Coverage

Units are sealed inside static-shielding antistatic packaging and packed inside heavy-wall shipping containers with custom foam dampening.

Every unit includes a comprehensive 12-month hardware replacement warranty covering functional performance and internal component reliability. Emergency orders process rapidly with international dispatch within 24 to 48 hours via premium express carriers like FedEx, UPS, or DHL.

Frequently Asked Questions (FAQ)

What is the conversion resolution of output channels on the 1756-OF8 module?

The module features 15-bit resolution across both ranges, delivering 320 µV per bit in voltage mode (+/-10V) and 650 nA per bit in current mode (0-20 mA).

Which removable terminal block options work with this analog module?

This unit requires either a 1756-TBNH 18-pin standard housing block or a 1756-TBSH 20-pin spring clamp terminal block for field wiring connections.

How does the module respond to an open-circuit fault in current mode?

When operating in current loop mode, internal electronics detect high resistance or broken wiring, triggering software fault bits inside the controller data table.

Can voltage and current output modes operate simultaneously on different channels?

Yes, each channel is independently configured within software, allowing a mix of voltage-driven drives and current-driven control valves on a single unit.

What is the standard order lead time and delivery schedule?

Shipments depart within 24 to 48 hours following order confirmation using express courier services including FedEx, UPS, and DHL.

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