The Allen-Bradley 1746-IV32 is a high-density digital input module for the SLC 500 PLC platform. It provides 32 input points designed for “Sourcing” (PNP) current logic.
Because it crams 32 points into a single-slot module, it uses a high-density 40-pin connector rather than the standard screw terminals found on lower-density modules.
1. Key Technical Specifications
The “IV” in the part number indicates Sourcing logic, meaning the module is designed to receive current from a sensor that “sources” power to the input terminal.
| Feature | Details |
| Number of Inputs | 32 |
| Voltage Category | 24V DC |
| Operating Voltage | 15V to 30V DC |
| Logic Type | Sourcing (PNP) |
| Backplane Current | 170mA at 5V / 0mA at 24V |
| Off-State Current | 1.5 mA (maximum) |
2. Wiring and the 40-Pin Connector
The most important thing to know about the 1746-IV32 is its wiring. You cannot wire it directly with standard screws. It requires:
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A 40-pin Wiring Harness: Usually the 1746-N3 (connector only) or a pre-wired cable.
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Interface Modules (IFMs): Many users prefer to use a 1794-IFM40 or similar terminal block that converts the 40-pin cable into standard screw terminals for easier maintenance.
Common Sourcing Logic (PNP)
Since this is a sourcing module, your sensors must be PNP.
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The sensor connects to the +24V DC supply.
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When triggered, the sensor sends the +24V signal into the module terminal.
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The module’s internal common is internally tied to the DC Ground (0V).
3. Addressing in RSLogix 500
Because it is a 32-point module, it occupies two full words (32 bits) in the Input Image Table. If the module is in Slot 3, its addresses will be:
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Word 0:
I:3.0/0throughI:3.0/15(Inputs 0–15) -
Word 1:
I:3.1/0throughI:3.1/15(Inputs 16–31)
4. Heat and Density Considerations
High-density modules generate more heat than 8 or 16-point modules.
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Surrounding Modules: Avoid placing high-power output modules directly next to the 1746-IV32 if your cabinet ambient temperature is high.
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Simultaneous On-State: Depending on your hardware revision and temperature, there may be limits on how many inputs can be “ON” at the same time at 30V DC. Check the technical data sheet if your application requires all 32 inputs to be high simultaneously in a hot environment.
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