Woodward 9905-971 Discrete Input Module

Woodward 9905-971 Discrete Input Module

The Woodward 9905-971, also cataloged as the Discrete Input Module, is a 24-channel input card designed for turbine and industrial control systems, providing fast update cycles and latent fault detection for high-reliability applications.

Hardware Specifications

Functional Description

• Latent Fault Detection: Each relay output is continuously tested without affecting its operational state. Series-parallel relay configuration ensures tolerance against single or dual relay failures.
• Relay Outputs: Configurable for normally open (NO) or normally closed (NC) contacts.
• Contact Wetting Voltage: 24 VDC internal supply or external 18–32 VDC / 100–150 VDC sources.
• Isolation: Fully isolated discrete inputs require common reference connection between input and power source.

Jumper & Wiring Requirements

• Internal 24 VDC wetting: Jumpers required between terminals 33, 34, and 35.
• External wetting: External source common must be tied to discrete input commons (terminals 34 and 35).
• Modules are secured with screws and disengaged via top/bottom handles for safe removal.

Frequently Asked Questions

Q: How many inputs does each module accept? A: Each module accepts six contact inputs, with four modules totaling 24 inputs.

Q: What is the contact wetting voltage? A: 24 VDC nominal, with options for external 18–32 VDC or 100–150 VDC sources.

Q: How does latent fault detection work? A: Relays are opened/closed in pairs or individually to verify state changes, with readback circuitry detecting errors.

Field Installation Guidelines

• Insert into card guides and secure with screws at top and bottom.
• Connect commons correctly to avoid floating inputs.
• Use shielded cabling for input wiring to minimize EMI.
• Validate relay outputs during commissioning with diagnostic readback.
• Ensure jumper configuration matches the selected wetting voltage source.