Allen-Bradley 1746-IV16 SLC 500 Discrete Input Module

The Allen-Bradley 1746-IV16, also cataloged as the 1746-IV16 Discrete input module, operates as a dedicated hardware component for 24 VDC voltage state sensing within SLC 500 platforms. The module provides direct signal conditioning, converting 16 independent binary inputs from field devices into logic-level signals readable by the processor across the chassis backplane.

Hardware Specifications

Backplane Bus Communication Velocity and Deterministic Timing

The electronic architecture of the assembly is optimized for high backplane bus communication velocity across the internal SLC chassis infrastructure. Input channel states are updated cyclically and synchronized with the processor scan via the internal 5 VDC logic rail, which demands a fixed 85 mA backplane current load. Firmware flash compatibility rules dictate that the module interfaces with all fixed and modular SLC 500 processors without requiring specific software driver modifications. This native integration ensures deterministic response times, maintaining a hardware signal propagation delay of 0.3 ms during off-to-on transitions and 0.5 ms during on-to-off transitions under maximum resistive load.

Frequently Asked Questions

Q: Does this module support hot-swapping or insertion under power (RIUP)?

A: No. The SLC 500 chassis backplane architecture does not support RIUP. Removing or inserting the module while the chassis is powered will disrupt backplane bus communication velocity and can cause permanent hardware damage or CPU faults.

Q: What is the operational distinction between this module and standard sinking input cards?

A: This module utilizes a sourcing wiring configuration. The input channels require the connected field device to source current from the positive potential (+VDC) line into the module terminal, establishing a common negative return path.

Field Installation Guidelines

• Chassis Alignment and Insertion: Power down the entire SLC 500 chassis before installation. Slide the module firmly into the selected slot alignment guides until the top and bottom retention tabs snap securely into the chassis frame.
• Wiring Separation Practices: Route all 24 VDC discrete input conductors through the lower wiring routing paths. Maintain separate physical wire runs from high-voltage AC conductors (such as 120 VAC lines) within the enclosure to minimize electromagnetic noise coupling.
• Terminal Block Engagement: Strip signal wires to the designated length and secure them into the removable terminal block assembly. Verify that screw terminals are torqued properly to ensure constant physical contact and prevent intermittent open-circuit faults.
• Grounding Continuity: Ensure the chassis itself is bonded to the main electrical enclosure ground bus using a low-impedance copper conductor to safeguard the internal backplane logic from transient surge currents.