Purchase now: Allen Bradley 1747-NO4I Analog Module
Purchase now: Atlantechdrives provides you the 1747-NO4I, a high-performance 4-channel analog output module designed by Allen Bradley for the SLC 500 automation platform. Often associated interchangeably with the 1746 I/O chassis architecture, this module is engineered to convert 14-bit digital values from the PLC processor into highly precise, continuous analog current signals. It is an absolutely essential hardware component for driving proportional hydraulic control valves, modulating variable frequency drives (VFDs), and commanding remote chart recorders in closed-loop control systems where absolute accuracy is required. The 1747-NO4I utilizes a robust digital-to-analog converter (DAC) that translates the integer value from the SLC processor into a highly linear, step-less analog wave. Because the backplane provides optical isolation, the delicate internal 5V DC communication bus is completely shielded from potential high-voltage transients that might strike the field wiring on the factory floor.
Technical Specifications of the 1747-NO4I
This module features four independent single-ended output channels, providing excellent signal resolution for delicate process adjustments.
- Part Number: 1747-NO4I (Compatible with SLC 500 systems)
- Module Type: Analog Output Module
- Signal Type: Current (mA)
- Number of Channels: 4 Single-ended outputs
- Output Ranges: 0 to 20 mA, 4 to 20 mA
- Resolution: 14-bit
- Maximum Load Impedance: 500 Ohms
- Backplane Current Draw: 55 mA at 5V DC
Expert Installation Advice: Loop Impedance and PID Scaling
When installing analog current modules, cable resistance is a critical factor. Expert Tip: The 1747-NO4I has a strict Maximum Load Impedance of 500 Ohms. This limit includes the internal resistance of your receiving device (like a VFD analog input) plus the total copper resistance of your wire run. If your total loop resistance exceeds 500 Ohms, the internal amplifier will not have enough electrical power to push a full 20 mA through the circuit, resulting in severe process control errors. Furthermore, when integrating the 1747-NO4I with a PID loop instruction in your RSLogix 500 program, ensure that the Control Variable (CV) output is correctly scaled. The module requires a specific integer range (usually 0 to 16383 or 6240 to 31200 depending on your data format) to correspond to the physical 4-20mA output. Scaling this incorrectly will cause your valves to over-saturate or fail to reach 100% stroke.
Maintenance and Power Supply Requirements
It is important to remember that this analog module requires an external 24V DC power supply wired directly to the front removable terminal block. The SLC chassis backplane provides the logic power, but it does not supply the current to generate the 4-20mA field signals. If all four channels fail simultaneously while the PLC remains in RUN mode, the most likely culprit is a blown fuse on the external 24V DC supply, rather than a failure of the module itself.
Frequently Asked Questions (FAQs)
Q: Can I output voltage with the 1747-NO4I?
A: No. The «I» in the part number dictates that this module is hardware-locked to generate Current (mA) only. If your application requires voltage (like 0-10V DC), you must use the NO4V module variant.
Q: Are the four output channels individually isolated?
A: No, the four output channels on this module are «single-ended,» meaning they all share a common internal ground return path.
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To complete your process control loop, this analog current output card is the functional counterpart to the 1746-NI4 input module.
