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Key Technical Specifications
- Catalog Number: 1746-IB16
- Manufacturer: Allen-Bradley
- Product Family: SLC 500
- Module Type: Digital DC input module
- Input Count: 16
- Input Type: Sinking
- Input Voltage Range: 10-30 V DC
- Nominal Input Voltage: 24 V DC
- Nominal Input Current: 8 mA at 24 V DC
- Backplane Current at 5 VDC: 50 mA
- Signal Delay: 8 ms ON, 8 ms OFF
- Isolation: 1,500 V AC backplane, 500 V DC communication circuits
Product Introduction
The Allen-Bradley 1746-IB16 is a 16-point sinking DC input module for the SLC 500 platform. It accepts 24 VDC field signals from sensors, push buttons, limit switches, and other discrete devices.
This module is a common legacy replacement in SLC 500 panels that need a 16-point DC input card. The 1746-IB16 is specified for 10-30 VDC input, 8 mA nominal current, and standard SLC 500 rack compatibility, so it fits established control cabinets without redesign.
Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| Input LED never turns on | Missing 24 VDC field supply | ✅ High | Measure 10-30 VDC at the input common with a meter | Check the sensor supply and field fuse first |
| Input LED on, PLC bit stays off | Slot mapping or processor logic issue | ⚠️ Medium | Verify the program address and rack location | Confirm the module is in the correct slot |
| One channel stuck ON | External device leaking voltage or shorted wiring | ✅ High | Remove the field wire and recheck the input status | Inspect the sensor or switch wiring before replacing the module |
| Several inputs dead at once | Common return open or field supply lost | ✅ High | Check the common terminal and supply feed continuity | Repair the common feed before condemning the card |
| Inputs flicker or chatter | Noisy wiring or marginal voltage | ✅ High | Measure field voltage under load and inspect cable shielding | Clean up wiring and verify supply stability |
| All inputs dead after swap | Wrong part number or no backplane power | ✅ High | Confirm the part number and measure rack power | Verify the chassis PSU and exact catalog number |
If you are stuck, send photos of the wiring, terminal block, and processor diagnostics to technical support.
1746-IB16
1746-IB16
Frequently Asked Questions
Q: What does the 1746-IB16 do?
It is a 16-point 24 VDC sinking input module for the SLC 500 PLC family.
Q: Is it an AC input card?
No. This is a DC input module. If your field devices are 120 VAC, you need an AC input module instead.
Q: What kind of devices does it read?
Typical uses are proximity switches, push buttons, limit switches, and other 24 VDC discrete signals.
Q: Is it still current production?
No. It is a legacy SLC 500 part, so most supply comes from surplus or refurbished stock.
Q: Can I replace it with a similar 1746 module?
Yes, if the voltage, sinking/sourcing style, and input count match. Do not assume another 1746 input card is equivalent without checking the wiring and logic.
Q: What usually gets blamed on the module when it is not the module’s fault?
Lost field power, bad commons, miswired sensors, or a PLC addressing issue. In the field, those are more common than a dead input card.
Q: What should I verify before ordering?
Check the exact part number, input type, voltage range, and the chassis slot. If the site is wired for 24 VDC sinking inputs, the 1746-IB16 is the right class of module, but the field wiring still needs a hard check.
