Schneider B351 Discrete Input Module

The Schneider B351, also cataloged as the B351 115VAC discrete input module, operates as a dedicated hardware component for converting 115 VAC field discrete signals into digital logic states within Modicon PLC processing racks.

Suffix Breakdown & Model Matrix

Hardware Specifications

Backplane Bus Communication Velocity & I/O Density Scaling

Engineered for industrial control environments, the Schneider B351 delivers optocoupler-based electrical isolation between high-voltage 115 VAC field circuits and low-voltage internal CPU backplane logic. The 8-channel input array features transient voltage suppression on each circuit to filter line noise, inductive kickback, and false switching states. Integrated field-side LED status indicators provide immediate visual verification of active input conditions, while deterministic backplane bus scanning ensures rapid status transfer to the central processor.

Frequently Asked Questions

Q: Can the Schneider B351 handle DC input voltages?

A: No, the B351 is designed specifically for 115 VAC discrete input signals and should not be wired to DC power sources.

Q: Are individual channels on the B351 optically isolated?

A: Yes, all eight 115 VAC input circuits feature optocouplers providing up to 1500 VAC isolation between field signals and internal PLC backplane logic.

Q: Does replacing a faulty B351 require re-wiring field conductors?

A: Field connections attach directly to screw terminals; wiring must be disconnected from the terminal strip during module replacement after shutting down rack power.

Field Installation Guidelines

Ensure all main rack AC supply and field circuit power sources are fully de-energized prior to installing or removing the B351 module. Mount the module firmly into its designated slot on the Modicon rack structure until locking mechanisms are securely engaged. Strip 115 VAC field wiring to recommended length and secure conductors to the screw terminal block, ensuring proper torque to avoid loose contacts. Route high-voltage AC cables away from low-voltage DC communication lines to prevent electromagnetic interference.