Woodward 9905-971 Discrete Input Module | 24 Channels | 9900 Series

Description

Product Overview

The Woodward 9905-971 is a Discrete Input Module from the 9900 Series. It reads 24 on/off signals from field devices. The module detects relay failures without stopping normal operation. This keeps your turbine control system safe and reliable.

Key Features at a Glance

• • 24 Discrete Input Channels

Each module accepts six contact inputs. Four modules give you 24 total channels.

• • Latent Fault Detection

Tests each relay in the background. Finds hidden faults before they cause a shutdown.

• • Fast Update Time

Scans all inputs in just 5 milliseconds.

• • High Resolution Time Stamping

Records event times with 1 millisecond accuracy.

• • Flexible Wetting Voltage

Use internal 24Vdc or external 18-32Vdc / 100-150Vdc power.

• • Fully Isolated Inputs

Each input channel has full electrical isolation.

Technical Specifications

• Brand: Woodward
• Part Number: 9905-971
• Series: 9900 Series
• Module Type: Discrete Input Module / Relay Input Module
• Number of Channels: 24
• Input Voltage: 24 Vdc per channel
• Update Time: 5 ms
• Time Stamping Resolution: 1 ms
• Contact Wetting Voltage (Internal): 24 Vdc
• External Power Options: 18-32 Vdc or 100-150 Vdc
• Repair Time: 3 to 7 days
• Country of Origin: United States (USA)
• Availability: In Stock

Performance Data

• Input Type: Dry contact or solid state
• Off-State Leakage: Less than 1 mA
• On-State Voltage Drop: Less than 2 Vdc
• Isolation Voltage: 1500 Vrms between channels
• Temperature Range: -40°C to +85°C (operating)
• Humidity Tolerance: 0 to 95% non-condensing
• Noise Immunity: Meets IEC 61000-6-2 standards

How Latent Fault Detection Works

• Each relay output uses six individual relays in series-parallel.
• When closed, all six relays close. One or two failures will not open the output.
• When open, all six relays open. One failure will not close the output.
• The module tests relays in pairs without changing the output state.
• Readback circuitry checks each relay contact’s actual position.
• The system reports any errors and stops testing if a fault occurs.
• Normal control operation continues during all tests.

Diagnostic Capabilities

• Latent fault detection runs automatically in the background.
• Readback verification for every relay contact.
• Error reporting without stopping the turbine.
• LED indicators show module health and channel status.

Typical Applications

• Turbine start/stop pushbutton monitoring.
• Emergency shutdown switch reading.
• Valve limit switch status inputs.
• Breaker position feedback.
• Safety interlock monitoring in power plants.
• Fault tolerant control systems that need high reliability.

Installation Guide

• Insert the module into card guides inside the 9900 chassis.
• Push firmly to connect the board to the motherboard.
• Secure with two screws (top and bottom of front panel).
• Use the two handles to pull the module out for removal.
• Toggle handles outward to disconnect from the motherboard.
• Connect wetting voltage to terminals 33, 34, and 35 as needed.

Wiring Instructions

• Using internal 24Vdc? Add jumpers between terminals 33, 34, and 35.
• Using external power? Connect the external source common to terminals 34 and 35.
• External power options: 18-32 Vdc or 100-150 Vdc.
• All discrete inputs share a common reference point.
• Use twisted pair wires for long runs over 100 meters.

Debugging & Maintenance Tips

• Check LED status after power-up. A steady green light means normal operation.
• Run latent fault detection once per month for critical systems.
• If you see a relay error, replace the module. Individual relays are not field repairable.
• Test each input channel with a known 24Vdc source yearly.
• Keep spare modules on hand for quick replacement.

Compatibility Information

• Designed for Woodward 9900 Series turbine control systems.
• Works with Modicon Quantum PLCs using a Woodward gateway. See Modicon Quantum Series for options.
• Replaces older 9900 series discrete input modules directly.
• Compatible with dry contacts and 24Vdc solid state outputs.
• Not for use with AC voltage inputs.

Certifications & Standards

• CE marked for European safety compliance.
• UL listed for industrial control equipment.
• RoHS compliant.
• Meets IEC 61000-6-2 immunity standards.

Packaging List

• 1 x Woodward 9905-971 Discrete Input Module
• 1 x 35-pin terminal block connector.
• 1 x Installation quick guide.
• No wiring jumpers included. Use standard 18 AWG wire.

Warranty & Shipping

• Warranty: 12 months from shipment date.
• Shipping Carriers: FedEx, UPS, DHL.
• Same-day shipping for in-stock orders before 2 PM EST.
• Repair Service: 3 to 7 days for factory repair.

Frequently Asked Questions (FAQ)

• • What is latent fault detection?

A background test that finds hidden relay failures. It checks each relay without changing the output state.

• Why do I need latent fault detection?

In fault tolerant systems, one hidden fault is okay. But a second fault can cause a sudden shutdown. Latent detection prevents this.

• How fast does this module scan inputs?

Every 5 milliseconds. Time stamps events at 1 millisecond resolution.

• My module shows a relay error. What should I do?

Replace the module. The error means at least one relay failed the self-test. Do not ignore this error.

• Can I use external wetting voltage?

Yes. Use 18-32 Vdc or 100-150 Vdc. Connect the external common to terminals 34 and 35.

• What happens if I do not use jumpers for internal power?

The inputs will not work. No voltage reaches the contacts. Add jumpers between 33, 34, and 35.

• Should I buy this or a standard input module?

Buy this for critical turbine applications that need high safety. For simple monitoring, a standard module costs less.

• How many modules can I put in one chassis?

Up to 16 modules. This gives you 384 discrete inputs per controller.

Selection Guide (Buying Advice)

• Count your on/off field devices first. Each device needs one channel.
• Need high reliability? Choose the 9905-971 with latent fault detection.
• Have AC sensors? This module does not work. Choose an AC input module instead.
• Need fast event recording? The 1 ms time stamping works perfectly.
• Avoid this module if you have analog sensors (4-20mA or 0-10V). Use the 9905-970 instead.
• Buy this module for new 9900 systems or as a direct replacement.
• For non-critical applications, a standard discrete input module costs less.

Need Help? Contact Us

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