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Key Technical Specifications
- Catalog Number: 1746-NI16I
- Manufacturer: Allen-Bradley
- Product Family: SLC 500
- Module Type: Analog input module
- Number of Channels: 16
- Input Types: 0-20 mA, 4-20 mA, ±20 mA, 0-1 mA
- Resolution: 16-bit
- Backplane Current at 5 VDC: 125 mA
- Backplane Current at 24 VDC: 75 mA
- Backplane Power Consumption: 2.425 W maximum
- Isolation: 500 V AC and 710 V DC for 60 s
- A/D Conversion: Sigma-Delta
Product Introduction
The Allen-Bradley 1746-NI16I is a 16-channel analog current input module for the SLC 500 platform. It reads current-loop signals such as 4-20 mA from process instruments and converts them into high-resolution PLC data.
This module is used when a panel needs dense analog input capacity without changing the SLC rack layout. The 1746-NI16I gives you 16-bit resolution, isolated channels, and multiple current ranges, which makes it a solid fit for process monitoring and legacy control systems.
1746-NI16I
1746-NI16I
Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| One channel reads 0 mA | Open loop, bad transmitter, or broken wire | ✅ High | Measure loop current in series with a meter | Check the instrument and field wiring first |
| All channels read low or zero | Missing loop power or common wiring issue | ✅ High | Verify loop supply voltage and commons | Restore field power before replacing the module |
| Channel value is noisy | Ground loop, shield issue, or unstable transmitter | ✅ High | Check cable shielding and compare with a known-good loop | Fix grounding and wiring before blaming the module |
| Reading is stuck at full scale | Shorted input, wrong range, or misconfigured scaling | ✅ High | Verify the selected input range and measure actual current | Confirm range setup and sensor output |
| Only one group fails | Group wiring or group common fault | ✅ High | Test the common terminal for that 4-channel group | Inspect the group common and terminal block |
| PLC sees module fault | Backplane, slot, or configuration problem | ⚠️ Medium | Reseat the module and verify rack status | Check chassis power and slot assignment |
If you are stuck, send photos of the wiring, loop supply, and processor diagnostics to technical support.
Frequently Asked Questions
Q: What is the 1746-NI16I used for?
It is an analog current input module for reading process signals such as 4-20 mA loops in an SLC 500 system.
Q: Is this a voltage input card?
No. This is the current-input version. If your instrument outputs voltage, this is not the right module.
Q: How many channels does it have?
It has 16 analog input channels.
Q: What signal ranges does it accept?
It supports 0-20 mA, 4-20 mA, ±20 mA, and 0-1 mA current inputs.
Q: Is it still current production?
No. This is a legacy SLC 500 part, so most units are surplus or refurbished.
Q: Why is analog replacement more sensitive than digital replacement?
Because scaling, loop power, shielding, and channel grouping all matter. A module can be healthy and still give bad readings if the loop wiring is wrong.
Q: What should I verify before ordering?
Check the exact part number, signal type, channel count, and loop wiring. For this card, the biggest mistake is buying it for a voltage loop or assuming the scaling will match automatically.
