Allen-Bradley 1756-OF6CI Overview
The Allen-Bradley 1756-OF6CI is a ControlLogix isolated analog output module designed for precise current control in demanding industrial environments. This module provides six individually isolated current outputs, making it an excellent choice for applications that require signal integrity and noise immunity. Engineers and system integrators often select this module for its robust feature set and reliable performance within the ControlLogix platform.
This module supports both integer and floating-point data formats, offering flexibility in how you configure and process control signals. It includes valuable features such as data echo, ramping/rate limiting, clamping/limiting, and hold for initialization. These capabilities help you manage output transitions smoothly and protect downstream equipment from sudden changes. The module also supports clamp/limit alarms, which alert operators when outputs reach predefined boundaries.
Key Technical Specifications
Understanding the technical specifications of the Allen-Bradley 1756-OF6CI helps you determine if it fits your application. The module draws 250 mA from the 5V backplane supply and 300 mA from the 24V backplane supply, with a maximum power dissipation of 4.9 W at 60°C. It requires a removable terminal block, either the 1756-TBNH or 1756-TBSH, for wiring connections.
The output range spans 0 to 20 mA, with a resolution of 13 bits across 21 mA, providing fine control. The module offers isolation voltage of 50V continuous, ensuring channel-to-channel separation. For communication, it supports both integer and floating-point formats, with a maximum scan time of 10 ms for integer and 25 ms for floating-point. The settling time is less than 2 ms to 95% of final value with resistive loads, which suits fast-moving processes.
Protection and Accuracy
The 1756-OF6CI includes 24V DC overvoltage protection and short circuit protection limited to 21 mA or less. It does not have open circuit detection, so you should account for that in your design. The module's calibrated accuracy is better than 0.1% of 4 to 21 mA at 25°C, with a calibration interval of 6 months. Gain drift is 60 ppm/°C nominal and 100 ppm/°C maximum, ensuring stable performance across temperature variations.
Practical Applications
Because of its isolated outputs, the Allen-Bradley 1756-OF6CI excels in applications where you need to drive analog devices like valves, actuators, or transducers that operate at different ground potentials. The isolation helps prevent ground loops and reduces electrical noise, which is critical in high-interference industrial settings. The module's fast settling time and high accuracy also make it suitable for closed-loop control systems that demand precise current outputs.
When integrating this module, you must use the appropriate removable terminal block (1756-TBNH or 1756-TBSH) and install it in a grounded chassis. The module is routine tested at 1350V AC for 2 seconds, with a continuous isolation voltage of 250V, ensuring robust electrical isolation.
Conclusion
The Allen-Bradley 1756-OF6CI delivers reliable, isolated analog output performance for ControlLogix systems. Its combination of six isolated channels, multiple protective features, and high accuracy makes it a strong candidate for process control and automation tasks. If you need a dependable current output module with excellent isolation, this module deserves your attention.