Woodward 9905-970 LinkNet RTD Input Module

Product Introduction & Engineering Value

The Woodward 9905-970 is a LinkNet distributed I/O module designed to bring six 100 Ω RTD temperature measurements into a compatible Woodward control system. This makes it a field-acquisition component rather than a governor, CPU, or standalone temperature controller.

The part is particularly relevant to legacy Woodward installations. Woodward has classified the LON-based LinkNet modules, including 9905-970, as obsolete, while retaining them as spare parts for existing systems. That makes exact-part-number identification important when maintaining installed equipment.

Technical Specifications

Woodward’s Product Manual 02879 lists 9905-970 in the LinkNet module summary as “100 Ω RTD Input,” with six available channels. The same manual distinguishes it from the 4–20 mA, thermocouple, discrete-input, and analog-output LinkNet modules.

Published electrical details

Secondary-market documentation commonly reports 24 VDC supply, with listings also giving a 33 kΩ signal input impedance. However, these values should be treated as secondary specifications unless confirmed against the documentation for the exact hardware revision.

One supplier specifically lists a Rev. K version of 9905-970. If you are replacing an installed module, match the complete nameplate and revision rather than assuming every 9905-970 listing represents identical hardware.

9905-970

9905-970

Field Application & the “Trench” Experience

A turbine control cabinet is showing an intermittent high-temperature alarm on one bearing channel. The DCS trend looks suspicious, but the turbine itself is operating normally. During troubleshooting, the technician isolates the problem to the remote RTD acquisition channel and identifies the installed module as Woodward 9905-970.

The replacement is not treated as a generic six-channel analog card. The technician first confirms that the field sensors are 100 Ω RTDs, checks the existing LinkNet node configuration, verifies the module identity, and then performs channel-by-channel resistance checks before reconnecting the control-system network.

That approach matters on legacy turbine systems. Installing a 4–20 mA or thermocouple LinkNet module in the same general cabinet location would not make it electrically interchangeable with the 9905-970.

Specific application scenarios

• Steam turbine bearing-temperature monitoring — six RTD channels for bearing metal-temperature measurements.
• Gas turbine auxiliary temperature monitoring — collecting RTD signals from lubrication or mechanical subsystems.
• Generator temperature monitoring — monitoring applicable RTD-equipped machine components.
• Turbine lube-oil systems — acquiring temperature signals used by the supervisory control system.

Transparency SOP: QA & Testing

For New Surplus 9905-970 inventory, the inspection should concentrate on both the RTD channels and the legacy LinkNet interface.

1. Part-number verification
Confirm 9905-970 on the manufacturer’s label and record the hardware revision and serial information.

2. Physical inspection
Inspect the enclosure, terminal connections, board surfaces, connectors, mounting hardware, and evidence of corrosion or previous installation.

3. RTD simulation
Use appropriate precision resistance simulation to represent the applicable 100 Ω RTD input conditions on each channel.

4. Channel verification
Check all six input channels rather than testing only one representative channel.

5. LinkNet communication check
Where compatible Woodward test equipment is available, verify that the module communicates correctly with the applicable LinkNet controller.

6. Documentation
Record channel test results, module revision, condition classification, photographs, and warranty terms.

A current secondary-market listing advertises a 12-month warranty, while other suppliers offer different terms. Warranty should therefore be explicitly stated on the quotation or purchase order.

The Veteran’s Tech Trap Guide

⚠️ Trap #1 — Do not confuse 9905-970 with a generic analog-input card.

Woodward specifically assigns this part to 100 Ω RTD input duty. The adjacent LinkNet part numbers have different functions: 9905-966/967 are thermocouple inputs, 9905-968/969 are 4–20 mA inputs, and 9905-971 is a discrete-input module.

⚠️ Trap #2 — The LinkNet platform is legacy hardware.

Woodward announced the obsolescence of the LON-based LinkNet nodes and related I/O controller hardware. The modules remained available as spare parts for existing systems, but a replacement project should not assume that new system designs will use the same architecture.

PRO TIP: If the application is a maintenance replacement, record the existing LinkNet node address and controller configuration before removing the old module.

⚠️ Trap #3 — Check the RTD wiring arrangement.

A 100 Ω RTD input is not automatically equivalent to every temperature transmitter or resistance sensor in the plant. Verify the installed sensor type and wiring arrangement before connecting it to the 9905-970.

⚠️ Trap #4 — Watch for bad secondary-market specifications.

Some online sellers describe 9905-970 as a generic six-channel analog-input module, while others publish unrelated electrical specifications. Woodward’s own manual gives the key identification: six-channel 100 Ω RTD input LinkNet module.

Dynamic FAQ

What is Woodward 9905-970?

It is a Woodward LinkNet 6-channel, 100 Ω RTD input module used for temperature-signal acquisition in compatible Woodward control systems.

How many RTD channels does 9905-970 provide?

The documented LinkNet configuration provides six RTD input channels.

Is 9905-970 a 4–20 mA input module?

No. Woodward’s LinkNet documentation distinguishes 9905-970 as the 100 Ω RTD input module. The 4–20 mA variants are separate part numbers.

Is 9905-970 obsolete?

Yes. Woodward’s product-change documentation lists the LON-based LinkNet modules, including 9905-970, among obsolete modules, while noting their continued availability as spare parts for existing systems.

Can a New Surplus 9905-970 be used as a replacement?

Potentially, provided the existing system uses the same LinkNet architecture and the module’s exact part number and revision are compatible. Confirm the RTD type, node configuration, controller compatibility, and hardware revision before installation.

What does “New Surplus” mean for this module?

It normally means unused original inventory that entered the secondary market through excess stock, project cancellation, or similar channels. It should be distinguished from Used and Refurbished equipment. A supplier should provide the exact condition, photos of the nameplate, test information, and written warranty terms.