Purchase now: Allen Bradley 1746-NO8I High-Density Analog Module
Purchase now: Atlantechdrives provides you the 1746-NO8I, a high-density analog output module manufactured by Allen Bradley for the SLC 500 series. This powerful unit doubles the output capacity of standard modules, delivering 8 independent channels of Current (mA) control from a single chassis slot. The 1746-NO8I is specifically engineered for large-scale process automation—such as water treatment plants, chemical dosing skids, and extensive boiler controls—where the PLC must simultaneously modulate numerous control valves, VFDs, and flow regulators using the robust, noise-immune 4-20mA standard.
Technical Specifications of the 1746-NO8I
By offering 8 channels, the 1746-NO8I frees up valuable rack space and significantly reduces the cost per channel. It delivers precise 16-bit resolution, ensuring that your PID loops have granular control over the final control elements, minimizing process overshoot and reducing mechanical wear on valves.
- Part Number: 1746-NO8I
- Module Type: High-Density Analog Output
- Signal Type: Current (mA) Only
- Number of Channels: 8 Single-ended outputs
- Output Ranges: 0 to 20 mA, 4 to 20 mA
- Resolution: 16-bit (Superior precision)
- Maximum Load Impedance: 500 Ohms
- Backplane Current Draw: 120 mA at 5V DC, 250 mA at 24V DC
- External Power Required: 24V DC
Expert Tips: Calculating Power Supply Requirements
High-density modules require careful power planning. Expert Tip: The 1746-NO8I relies on an external 24V DC power supply to generate the current for all 8 loops. If you are commanding all 8 channels to output 20 mA simultaneously, the module is pushing 160 mA of current purely to the field devices, on top of the power required to run the module’s internal amplifiers. If your external 24V DC power supply is undersized or shared with heavy inductive loads (like solenoids), a voltage dip will cause all 8 analog outputs to drop simultaneously, leading to a catastrophic multi-system failure. Always dedicate a clean, appropriately sized 24V DC power supply to your analog I/O racks.
Maintenance and Step Response
The 1746-NO8I offers a very fast step response time, making it suitable for highly dynamic processes. During routine maintenance, inspect the removable terminal block (RTB) wiring. Because 8 channels require 16 individual wires plus power connections packed into a single RTB, the wiring can become extremely dense. Ensure no copper strands are touching adjacent terminals, which would short the current loops together. If an output seems stuck, verify the channel isn’t being overwritten by a conflicting OTE instruction in your ladder logic.
Frequently Asked Questions (FAQs)
Q: Are the 8 channels individually isolated?
A: The 1746-NO8I provides excellent optical isolation between the field wiring and the PLC backplane. However, the 8 output channels are «single-ended,» meaning they share a common return internally. They are not individually isolated from each other.
Q: Can I output voltage on any of these 8 channels?
A: No, the 1746-NO8I is strictly a current-generating module (mA). If your application requires high-density voltage outputs, you would need a different module like the 1746-NO8V.
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For expanded current loop control, this 8-channel card pairs effectively with the high-capacity 1746-A10 modular rack.
