Description
Product Introduction
The Allen-Bradley 1746-IV16 is a high-density, 16-point 24V DC sourcing digital input module designed for the SLC 500 programmable logic controller system. Installed into any standard slot of a 1746 chassis (such as a 1746-A7 or 1746-A10 rack), the module interfaces low-voltage 24V DC field devices with the SLC CPU backplane.
Featuring optical isolation between field wiring and internal backplane circuitry, the 1746-IV16 protects the controller from electrical noise, spikes, and ground loops. Its 16-point sourcing configuration (current flows out of the module terminal to the field device) makes it the standard choice when connecting NPN (sinking) 3-wire DC sensors or grounding-type field contacts to an SLC 500 rack.
Key Technical Specifications
| Parameter | Specification |
| Manufacturer Part Number | 1746-IV16 |
| Number of Inputs | 16 Digital DC Inputs (Sourcing) |
| Voltage Category | 24V DC Source |
| Operating Voltage Range | 10 to 30V DC at 50°C / 10 to 26.4V DC at 60°C |
| Off-State Voltage (Max) | 5V DC |
| On-State Current (Min) | 3.0 mA at 10V DC |
| Nominal Input Current | 8 mA at 24V DC |
| Backplane Current Draw | 85 mA at 5V DC / 0 mA at 24V DC |
| Signal Delay (Max) | Turn-On = 8 ms, Turn-Off = 8 ms |
| Points per Common | 16 Points on 1 Common |
| Operating Temperature | 0°C to 60°C (32°F to 140°F) |
Application Scenarios & The “Trench” Experience
It is 1:30 AM on an imported automated assembly line built around Japanese OEM specifications (where NPN/sinking sensors are standard). A key photoelectric part-presence eye fails on Input Bit 7, halting the index turntable. The technician needs to replace the card, but rewiring 16 field sensors to PNP would require hours of panel modifications. Thanks to the 1746 removable terminal block (RTB), the tech turns off panel power, swings the pre-wired terminal arm free, swaps in a bench-tested 1746-IV16 from spares, snaps the RTB back into place, and powers up—restoring NPN sensor tracking in under 5 minutes without touching a single field wire screw.
- NPN Sensor Networks – 3-Wire NPN Photoelectric & Proximity Sensors – Native sourcing inputs provide the ground path required for sinking NPN outputs.
- Ground-Switched Field Circuits – Pull-to-Ground Limit Switches & Contacts – Ideal for safety or interlock circuits that trigger by pulling the input channel to 0V DC Common.
- High-Density DC Panel Retrofits – SLC 5/03, 5/04, 5/05 Systems – Doubles DC input capacity over 8-point modules (like 1746-IV8) within a single rack slot.
- 1746-IV16
- 1746-IV16
Transparency SOP: Quality Assurance & Testing
We don’t just ship boxes; every 1746- module undergoes thorough diagnostic bench testing prior to dispatch.
- Inbound Physical & Terminal Audit: Inspected housing plastics, backplane edge connector pins, and terminal block screw threads for signs of wear or corrosion.
- Backplane Logic Verification: Installed into an active 1746-A10 rack; verified 85 mA backplane current consumption and proper CPU card detection without backplane communication errors.
- 16-Channel Sourcing Signal Testing: Connected each of the 16 channels to a 0V DC ground reference individually; verified LED status illumination and RSLogix 500 input data table updating (
I:e.0throughI:e.15). - Off-State Threshold Check: Verified that voltages above 5V DC (relative to 0V ground) properly register as OFF to ensure immunity against stray field noise.
- ESD Protection & Packaging: Cleaned, wrapped in antistatic shielding wrap, and packaged inside shock-absorbing foam containers.
The Veteran’s Tech Trap Guide (Crucial Value-Add)
- ⚠️ Source vs. Sink Wiring (NPN Sensors Required)!
The 1746- is a sourcing input module (current flows out of the module terminals to ground). Connected 3-wire DC sensors must be NPN (sinking) outputs, which switch the signal line to 0V DC Common. Connecting PNP (sourcing) sensors will NOT trigger the input channels! (For PNP sensors, use a sinking input card like the 1746-IB16).
- ❗ Never Hot-Swap Modules in a 1746 Chassis!
Like all SLC 500 components, inserting or removing the 1746- while rack power is applied will cause electrical arcing across backplane pins, potential CPU memory corruption, or permanent board damage. Always isolate main rack power prior to swapping modules.
- ⚠️ Common Terminal Polarity (+24V DC Required on Common)
All 16 input channels share a single common return line (Terminal 17). For sourcing inputs, +24V DC must be connected to Terminal 17 to supply power to the internal input circuitry.
- ❗ Temperature Derating at 60°C
If operating in hot enclosures near the 60°C (140°F) ambient limit, the maximum field input voltage range drops from 30V DC down to 26.4V DC to prevent internal thermal overload.
Frequently Asked Questions (FAQ for Conversion)
Q: What is the primary difference between 1746-IB16 and 1746-?
A: The 1746-IB16 is a sinking DC input card (requires PNP sensors that supply +24V DC). The is a sourcing DC input card (requires NPN sensors that switch to 0V DC Common).
Q: What is the difference between 1746-IV8 and 1746-?
A: The 1746-IV8 provides 8 digital 24V DC sourcing inputs, while the provides 16 digital 24V DC sourcing inputs within the same single-slot card footprint.
Q: Does the module come with the removable terminal block (RTB)?
A: Yes, all our New Surplus and Refurbished 1746- modules include the front removable terminal block assembly.
Q: Are 1746- modules still manufactured by Allen-Bradley?
A: The SLC 500 platform has matured into legacy/discontinued status by Rockwell Automation. We maintain extensive stock of certified New Surplus and fully bench-tested, refurbished original 1746- modules.
Q: What warranty is provided with this module?
A: Every Allen-Bradley 1746- input module includes a full 12-month replacement warranty. If any input channel or backplane interface fails under standard operating conditions within one year, we send an immediate replacement from stock.
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