Introduction
When a production line stops because a PLC input card fails, every minute of downtime costs money. The Allen-Bradley 1746-IB16 is a proven SLC 500 digital DC sinking input module built to get your system back online quickly. This medium-density module provides sixteen discrete input channels in a single group with one common terminal, making it a practical replacement for existing SLC 500 racks.
What Is the 1746-IB16?
The 1746-IB16 is part of the Allen-Bradley SLC 500 series, manufactured by Rockwell Automation. It interfaces field devices that supply a signal voltage between 10 and 30 VDC to each input channel. The module uses sinking wiring configuration only. You can install it in any available I/O slot of a 1746 chassis, either locally alongside the CPU or in a distributed I/O chassis using a communication adapter.
Key Technical Specifications
Understanding the core ratings helps you confirm this module fits your application before you order.
Input Voltage and Current
The module operates at a nominal input voltage of 24 VDC with an operating range of 10-30 VDC. Nominal input current is 8 mA at 24 VDC. The OFF-state voltage maximum is 5.0 VDC, and OFF-state current maximum is 1 mA. These values ensure reliable signal detection from switches, proximity sensors, and auxiliary relay contacts.
Signal Response
Signal delay is 8 ms for ON and OFF transitions. The step response is 100 milliseconds in and 2.5 milliseconds out. This timing suits general-purpose DC input applications where moderate response speed is acceptable.
Backplane and Thermal Load
The module draws 0.050 A backplane current at 5 VDC. Thermal dissipation is 0.20 Watts per channel, with total module heat dissipation of 3.6W. Plan your enclosure ventilation accordingly.
Environmental Ratings
Operating temperature ranges from 0 to 60 °C (32 to 140 °F) at 5-95% relative humidity. Storage temperature ranges from -40 to 85 °C (-40 to 185 °F). The module withstands 30G operational shock and 2.5G vibration at 57-200 Hz.
Isolation and Certifications
The 1746-IB16 offers electro-optical isolation tested at 1500V between input terminals and control logic. It carries UL, CSA, and CE certifications, plus UL-A196, CSA, and C-UL Class I, Division 2 hazardous environment ratings.
Replacement and Upgrade Guide
If you are replacing a failed SLC 500 input module, the 1746-IB16 is a direct fit for any 1746 chassis. Before ordering, verify your existing module’s part number matches. Check that your CPU supports the required number of I/O points. Confirm whether your installation uses local or distributed I/O, since distributed setups require a 1746 communication adapter such as Remote I/O or Ethernet.
The module includes status LED indicators for each input channel, which simplify troubleshooting after installation. The removable terminal block allows quick module replacement without rewiring every field connection. This design reduces mean time to repair and keeps your line running.
Compatibility and Integration
The 1746-IB16 works with any SLC 500 chassis and CPU that supports the required I/O count. For I/O connection, use 1746-HT or 1746-HCA cables. The module communicates through the backplane, drawing 0.050 A at 5 VDC. In distributed configurations, pair it with a 1746 communication adapter for Remote I/O or Ethernet networks.
Typical field devices include limit switches, proximity sensors, pushbuttons, and auxiliary contacts from relays and contactors. The sinking configuration means field devices supply positive voltage to the input terminal, and the module completes the circuit to common.
Installation and Setup
Mount the module in any available slot of your 1746 chassis. Ensure the chassis power supply can handle the additional 0.050 A backplane load. Wire field devices according to sinking input requirements. Use the removable terminal block for clean terminations. After installation, verify each channel’s LED indicator responds correctly when the field device actuates.
Allow adequate clearance for airflow. The module dissipates 3.6W total, so enclosure temperature must stay within the 0 to 60 °C operating range. Avoid mounting near heat sources that could push ambient temperature beyond rated limits.
Maintenance and Reliability
Inspect the module periodically for loose terminal connections and LED function. The electro-optical isolation at 1500V protects control logic from field transients, contributing to long service life. In dirty environments, keep the enclosure sealed to maintain the 5-95% relative humidity rating. Follow your plant’s standard electrical safety procedures during any inspection.
Buyer’s Checklist
Before purchasing the 1746-IB16, confirm these points:
- Your application requires 16 sinking DC input channels
- Field device voltage falls within 10-30 VDC
- Your chassis has an available I/O slot
- Your CPU supports the additional I/O count
- You have the correct 1746-HT or 1746-HCA connection cable
SpareTechPLC supplies industrial automation parts and news for maintenance teams. Verify current lifecycle status and availability with SpareTechPLC before ordering.
Frequently Asked Questions
What voltage range does the 1746-IB16 accept?
The module accepts 10-30 VDC with a nominal input voltage of 24 VDC.
How many input channels does this module have?
It provides sixteen discrete sinking input channels in one group with a single common terminal.
Can I use this module in a distributed I/O setup?
Yes. Install it in a distributed chassis with a 1746 communication adapter such as Remote I/O or Ethernet.
What is the signal delay time?
Signal delay is 8 ms for both ON and OFF transitions.
Is the 1746-IB16 suitable for hazardous locations?
Yes. It carries UL-A196, CSA, and C-UL Class I, Division 2 hazardous environment ratings.
