Purchase now: Allen Bradley 1746-NO4I Analog Output Module
Purchase now: Atlantechdrives provides you the 1746-NO4I, a highly reliable 4-channel analog output module engineered by Allen Bradley specifically for the SLC 500 automation platform. This module is dedicated entirely to generating precise Current (mA) signals. It is an essential hardware component for industrial closed-loop control systems, translating the digital commands from the PLC processor into continuous 4-20 mA or 0-20 mA analog currents. The 1746-NO4I is widely utilized across manufacturing facilities to drive proportional control valves, modulate variable frequency drives (VFDs), and command remote chart recorders with exceptional accuracy.
Technical Specifications of the 1746-NO4I
The 1746-NO4I features a robust 14-bit digital-to-analog converter (DAC), ensuring smooth, stepless signal generation for delicate process adjustments. Unlike voltage modules, current outputs are highly immune to electrical noise and voltage drop over long cable runs.
- Part Number: 1746-NO4I
- Module Type: Analog Output Module
- Signal Type: Current (mA) Only
- 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, 195 mA at 24V DC
- External Power Required: 24V DC (for output channels)
Expert Installation Advice: Managing Loop Impedance
A common mistake when deploying analog current outputs is ignoring the total resistance of the field circuit. Expert Tip: The 1746-NO4I has a strict Maximum Load Impedance of 500 Ohms. This includes the internal resistance of the receiving device (like a VFD analog input) plus the resistance of the copper wire itself. If your total loop resistance exceeds 500 ohms, the module’s internal 24V amplifier will not have enough electrical «push» to drive a full 20 mA through the circuit. The result? Your PLC will output 100% in the logic, but the valve will only open to 85%, causing massive process control errors. Always calculate your loop resistance before commissioning long cable runs.
Maintenance and Power Supply Sizing
It is critical to remember that the 1746-NO4I requires an external 24V DC power supply wired directly to the front removable terminal block. The PLC chassis backplane does not provide the power to generate the 4-20mA field signals. During maintenance, if all 4 channels fail simultaneously, the most likely culprit is a tripped fuse or failure on this external 24V DC supply, rather than the module itself.
Frequently Asked Questions (FAQs)
Q: Can I configure one channel for voltage and the others for current?
A: No. The «I» in the 1746-NO4I part number indicates it is hardware-locked to generate Current (mA) only across all 4 channels. For voltage, you need the 1746-NO4V.
Q: Does this module require a separate Removable Terminal Block (RTB)?
A: Yes, it utilizes a standard Allen Bradley RTB, which allows you to pre-wire the panel and easily swap out the module without disturbing the field connections.
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For high-precision current regulation, this analog output module is technically optimized for use within a 1746-A7 7-slot chassis.
