WOODWARD 9905-971 LinkNet 16-Channel Discrete Input Module

Overview

Core Technical Specifications

1. Electrical Parameters

• Model: 9905-971, LinkNet Discrete Input Module
• Power supply: 18–32 VDC, typical power consumption 14.2 W
• Input channel: 16 independent digital DI channels
• Input signal type: 0–24VDC active signal / dry NO/NC contact, configurable sink/source mode
• Channel isolation: Each channel isolated by optocoupler, isolation voltage 2.5 kV
• Signal response speed: Scan cycle <1 ms, single channel response <10 ms
• Communication bus: Woodward proprietary LinkNet bus for interconnection with main controller
• Support Modbus RTU over RS485 for upper DCS/SCADA data upload

2. Mechanical & Environmental

• Mounting: Standard 35mm DIN rail rack installation
• Dimension: 160 mm × 100 mm × 60 mm
• Net weight: ~0.51 kg
• Operating temperature: -40 ℃ ~ +70 ℃
• Max ambient working temperature (continuous): 55 ℃
• Protection grade: IP20 (cabinet internal installation only)
• Compliance: MIL-STD-810 vibration & shock resistance standard, conformal coated PCB for anti-humidity, anti-oil mist
• Origin: United States

3. Diagnostic & Indication

• Per-channel LED status indicator: Green = signal ON, OFF = no input
• Module fault LED: Alarm for bus communication failure, overvoltage, short circuit
• Built-in self-test function, record timestamp fault logs for maintenance tracing

Main Functions

1. Field discrete signal centralized acquisition
    
   Collect all on-site switch status of prime mover units: emergency stop button, safety door interlock, oil pressure switch, exhaust temperature alarm, generator breaker auxiliary contact, vibration trip signal, valve limit feedback.
2. Isolated signal transmission to main governor
    
   Optical isolation eliminates interference between field strong electric signals and turbine control core, prevent surge damage to main controller CPU.
3. LinkNet bus distributed expansion
    
   Expand the limited DI channels of Woodward 505, 2301A speed governors; multiple 9905-971 modules can be cascaded on one LinkNet bus to expand I/O capacity.
4. Fault signal upload to upper monitoring system
    
   Convert discrete switch signals into digital data, uploaded via Modbus RTU to DCS, PLC or HMI for remote equipment status monitoring and alarm display.
5. Safety interlock signal transfer for turbine protection
    
   Transmit critical safety trip signals (overspeed pre-alarm, low lubricating oil pressure, high exhaust temperature) to governor logic to realize automatic unit shutdown protection.

Advantages

• 16-channel high-density integration, saves cabinet layout space compared with single-channel signal boards
• Independent optocoupler isolation per channel, single-loop short circuit will not affect other signal loops
• Wide operating temperature range, adapts to power plant, offshore platform, marine engine room harsh high-temperature & vibration environment
• Conformal coating circuit board, anti-corrosion, anti-moisture, suitable for oil & gas chemical working conditions
• Fast LinkNet bus communication, low signal delay, guarantee real-time safety interlock response
• Complete channel-level diagnosis, LED direct display fault point, greatly shorten on-site troubleshooting time
• Perfect matching with all mainstream Woodward turbine/generator governors, unified system spare parts management