DS3800DSFC1A1A GE

Technical Specifications

• Product Type: Servo Feedback Conditioning Board (Revision 1A1A)

• Part Number: DS3800DSFC1A1A

• Manufacturer: General Electric (GE)

• System Compatibility: GE Speedtronic Mark IV Turbine Control Systems

• Input Channels: 8 differential feedback inputs

• Input Types: LVDT, RVDT, Resolver

• Excitation Output: Fixed 5Vrms @ 2.5kHz (selectable via jumpers for 2.5kHz or 5kHz)

• Demodulation: Synchronous demodulation with fixed phase correction (factory-set)

• Output: ±10Vdc analog signal per channel

• Filtering: Fixed low-pass filter at 100Hz (hardware)

• Isolation: 1500Vrms opto-isolation

• Temperature Range: 0°C to +60°C

• MTBF: > 150,000 hours (MIL-HDBK-217F)

Key Features & Advantages

• Field-Proven Reliability: The GE DS3800DSFC1A1A uses discrete through-hole components with a long track record in GE turbines worldwide. This revision is known for its robustness and repairability.

• Fixed but Reliable Excitation: Factory-set 5Vrms @ 2.5kHz (jumper-selectable to 5kHz) provides stable excitation for most standard LVDT/RVDT sensors.

• Synchronous Demodulation: The GE DS3800DSFC1A1A uses analog synchronous demodulation, ensuring < 0.05% linearity error and < 0.02% per °C drift.

• Fixed Phase Correction: Factory-optimized phase compensation eliminates the need for field adjustment in most applications.

• Diagnostic LEDs: Front-panel LEDs indicate excitation presence, signal amplitude, and fault status for each of the 8 channels.

• Compact 8-Channel Design: Supports multiple feedback devices on a single board, saving rack space.

Typical Application Cases

• Servo Valve Position Feedback: Conditions LVDT signals from servo valves, providing position feedback to the Mark IV processor for closed-loop control.

• Actuator Stroke Monitoring: Processes RVDT signals from hydraulic actuators on steam turbine main stop and control valves.

• IGV Position Sensing: Conditions feedback from inlet guide vane position sensors in gas turbine compressors.

• Thrust Bearing Monitoring: Monitors LVDTs measuring turbine thrust position, detecting axial movement and preventing bearing failure.

Competitive Comparison

The GE DS3800DSFC1A1A is a simpler, fixed-configuration version of the base DS3800DSFC. It offers proven reliability for standard LVDT/RVDT applications but lacks the flexibility of later revisions.

Selection Guidelines & Precautions

1. Feedback Device Verification: Confirm your LVDT/RVDT specifications (primary impedance, excitation requirements) match the GE DS3800DSFC1A1A fixed 5V excitation. If your sensor requires different voltage or frequency, use a later revision instead.

2. Phase Correction: The GE DS3800DSFC1A1A has fixed phase compensation. If your feedback sensor has unusual electrical characteristics (e.g., long cable runs > 100m), verify demodulator output with an oscilloscope. Consider upgrading to a programmable revision if phase error is significant.

3. Filter Limitation: Fixed 100Hz filtering may not remove all high-frequency noise in environments with VFDs or ignition transformers. For noisy installations, consider adding external filters or upgrading to a revision with adjustable filtering.

4. Cable Shielding: Use shielded twisted-pair cables for all feedback connections. Ground shield at the GE DS3800DSFC1A1A end only to prevent ground loops.

5. ESD Handling: Use ESD-safe practices; contains sensitive analog front-end components.

6. Commissioning: Verify output voltage corresponds correctly to LVDT position using a calibrated position simulator. Use diagnostic LEDs to confirm excitation presence on all 8 channels.

7. Sourcing: Obsolete. Request functional test report including:

   • All 8 channels tested with LVDT/RVDT simulator

   • Excitation voltage and frequency verification

   • Demodulation linearity test (< 0.05% error)

   • Output offset and gain calibration

8. Spare Strategy: Keep one spare GE DS3800DSFC1A1A on-site. For turbines with critical feedback loops, consider redundant feedback conditioning using two boards in parallel.