Allen-Bradley 1756-OF8I – 8-Channel Isolated Analog Output Module | ControlLogix 1756 Platform
Engineering Background
The 1756-OF8I is a high-density isolated analog output module designed for the Allen-Bradley ControlLogix 1756 backplane architecture. Engineered by Rockwell Automation, it delivers eight independently isolated current/voltage output channels, enabling precise process control in demanding industrial environments where channel-to-channel isolation is critical to signal integrity and equipment protection.
Product Positioning
Targeted at process engineers and system integrators requiring reliable multi-channel analog output within a ControlLogix chassis, the 1756-OF8I is the preferred choice for applications in oil & gas, chemical processing, power generation, and advanced manufacturing where loop isolation eliminates ground loops and protects field instrumentation.
Complete Technical Specifications
| Parameter | Specification |
|---|---|
| Catalog Number | 1756-OF8I |
| Series | ControlLogix 1756 |
| Manufacturer | Rockwell Automation / Allen-Bradley |
| Module Type | Analog Output, Isolated |
| Number of Channels | 8 (individually isolated) |
| Output Signal Range (Voltage) | ±10V DC |
| Output Signal Range (Current) | 0–20 mA / 4–20 mA |
| Resolution | 16-bit |
| Channel Isolation | Channel-to-channel isolated (500V AC) |
| Update Rate | Configurable per channel |
| Backplane Current Draw (5V) | 250 mA |
| Backplane Current Draw (24V) | 2 mA |
| Field-Side Power | External 24V DC required |
| Operating Temperature | 0°C to 60°C (32°F to 140°F) |
| Storage Temperature | -40°C to 85°C |
| Relative Humidity | 5–95% non-condensing |
| Dimensions (H × W × D) | 94.0 × 94.5 × 69.6 mm |
| Approximate Weight | 260 g |
| Certifications | UL, CE, C-Tick, FM Class I Div 2 |
| Compatible Chassis | 1756-A4, A7, A10, A13, A17 and all ControlLogix chassis |
| Programming Software | Studio 5000 Logix Designer / RSLogix 5000 |
Proven Application Environments
- Oil & Gas: Valve positioner control and flow regulation loops requiring isolated 4–20 mA signals
- Chemical Processing: Multi-loop reactor temperature and pressure setpoint output with ground-loop immunity
- Power Generation: Turbine governor and excitation control with high-resolution voltage output
- Water & Wastewater: Pump speed reference and dosing control via isolated current loops
- Automotive Manufacturing: Precision motion and tension control in multi-axis servo systems
- Pharmaceutical: Batch process setpoint delivery with channel isolation for GMP compliance
Engineering Advantages
- True Channel-to-Channel Isolation: 500V AC isolation per channel eliminates ground loops and protects field devices from common-mode interference
- 16-Bit Resolution: Delivers 0.0015% full-scale accuracy for tight process control tolerances
- Flexible Output Modes: Supports voltage (±10V) and current (0–20 mA / 4–20 mA) per channel, configurable in software
- Fault State Configuration: Programmable hold-last-state or go-to-safe-value on controller fault for process safety
- Hot-Swap Capable: Removable terminal block (RTB) allows field wiring to remain intact during module replacement
- Diagnostics: Real-time open-wire detection and over-range/under-range alarming via RSLogix 5000 / Studio 5000
System Architecture & Signal Flow
The 1756-OF8I resides in any slot of a ControlLogix 1756 chassis and communicates over the ControlLogix backplane at full backplane bandwidth. The controller (e.g., 1756-L8x or 1756-L7x) writes output data to the module’s output image table via the I/O tree in Studio 5000. Each channel’s D/A converter independently converts the 16-bit digital word to an isolated analog signal. Field wiring connects via a 1756-TBCH or equivalent RTB. External 24V DC field power is required and must be fused per channel for protection.
Signal Flow: Controller Output Image → Backplane → 1756-OF8I DAC → Isolated Output Driver → Field Device (Valve / VFD / Transmitter)
Sourcing & Quality Verification
- All units sourced from authorized distributors or verified surplus channels with documented chain of custody
- Each module undergoes visual inspection, firmware version verification, and functional bench test prior to shipment
- Original Rockwell Automation firmware and configuration preserved — no third-party modifications
- Packaging inspected for tamper evidence; serial numbers cross-referenced against known counterfeit databases
- Certificate of conformance available upon request for regulated industries
Procurement Process
- Confirm Compatibility: Verify your ControlLogix chassis series and controller firmware revision against Rockwell’s Product Compatibility and Download Center (PCDC)
- Request Quote: Contact support@konmask.com or call +0086 19859288691 for volume pricing and lead time
- Order Placement: Purchase directly via Konmask.com with secure checkout; PO and wire transfer accepted for B2B orders
- Shipping: DHL / FedEx Express worldwide; export documentation and commercial invoice provided
- After-Sales Support: Technical assistance available for installation, configuration, and Studio 5000 add-on instruction (AOI) setup
Technical FAQ
Q: Can the 1756-OF8I be used in a 1756-A4 chassis with a 1756-L85E controller?
A: Yes. The 1756-OF8I is compatible with all ControlLogix 1756 chassis and all 1756 Logix controllers running RSLogix 5000 v16 or later / Studio 5000 v21 or later.
Q: Does each channel require individual external power?
A: The module requires a single 24V DC external field power supply connected to the RTB. Internal circuitry distributes and isolates power to each channel independently.
Q: What happens to outputs during a controller fault?
A: Each channel can be independently configured to hold last state, go to a user-defined safe value, or ramp to zero — configurable in the module properties within Studio 5000.
Q: Is the 1756-OF8I RoHS compliant?
A: Consult the Rockwell Automation Product Environmental Compliance page or contact us for the specific revision’s compliance documentation.
Q: What is the difference between 1756-OF8 and 1756-OF8I?
A: The “I” suffix denotes individually isolated channels. The standard 1756-OF8 is non-isolated. For applications with ground loop concerns or mixed field device grounding, the 1756-OF8I is strongly recommended.
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