GE DS200NATOG3A
GE DS200NATOG3A - Image 2

GE DS200NATOG3A

  • Product Overview: The DS200NATOG3A is an 8-channel analog output board for GE Mark V and Mark VI speedtronic control systems. It provides isolated 4–20 mA or 0–10 VDC output signals for controlling final control elements such as control valves, damper actuators, and variable frequency drives. Each channel is independently configurable and fully isolated from the others and from the backplane logic.
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Category: SKU: GE DS200NATOG3A

Description

GE DS200NATOG3A

  • Technical Specifications:
    • Channels: 8 independent analog output channels
    • Output Types: 4–20 mA (2-wire, loop-powered) or 0–10 VDC (4-wire)
    • Output Range: User-programmable per channel (e.g., 4–20 mA = 0–100% valve stroke)
    • Resolution: 12-bit D/A converter (4096 steps)
    • Accuracy: ±0.1% of full scale (typical); ±0.2% after 5 years
    • Update Rate: 10 ms per channel (all 8 channels updated simultaneously)
    • Isolation: 500 channel-to-channel; 500 VDC channel-to-logic
    • Load Capability: 4–20 mA output can drive up to 600 ohms loop resistance; 0–10 output can drive 10 kΩ minimum load
    • Power Supply: +5 VDC from backplane; 4.0 W typical power consumption
    • Diagnostics: Per-channel LED; loop fault detection (open circuit, short circuit); output saturation detection
  • Functional Features:
    • Independent Configuration: Each of the 8 channels can be set to a different output type (some 4–20 mA, some 0–10 ) without affecting other channels
    • Fail-Safe Output: Configurable fail-to-zero (output goes to 0% on fault), fail-to-last (output holds last value), or fail-to-midscale (output goes to 50%)
    • Loop Monitoring: Continuous monitoring of output loop for open circuit (wire break) and short circuit (output shorted to ground or supply)
    • Ramp/Slew Rate: Programmable ramp rate from 0.1%/second to 100%/second for smooth valve movement and to prevent water hammer
    • Initialization: On power-up, all outputs can be forced to a user-defined safe value (e.g., 0% for control valves, 100% for damper actuators)
  • Application Scenarios:
    • Steam Turbines: Control valve position command for throttle and governor valves; boiler feedwater regulating valve
    • Gas Turbines: Fuel valve position; inlet guide vane position; exhaust temperature control damper
    • Power Plants: Condenser cooling water valve; deaerator level control valve; chemical dosing pump speed
    • Oil & Gas: Pipeline flow control valve; tank level control valve; flare damper position
    • Water Treatment: Chemical feed pump speed; filter backwash valve; clarifier sludge valve
  • Performance Parameters:
    • Operating Temperature: 0°C to 60°C
    • Storage Temperature: -40°C to 85°C
    • Relative Humidity: 5% to 95% non-condensing
    • MTBF: Greater than 170,000 hours
    • EMC Compliance: IEC 61000-6-2, IEC 61000-6-4
  • Material & Structure:
    • Form Factor: Mark V/VI standard, approximately 170 mm × 100 mm × 25 mm
    • Connectors: 32-pin backplane connector; 8 × 4-pin field terminal blocks (one per channel) on top
    • PCB: 6-layer FR-4 with conformal coating
    • Enclosure: Zinc-plated steel with EMI shielding
    • Weight: Approximately 320 grams
    • Front Panel: 8 green LEDs (one per channel, indicates output active); 1 amber fault LED; 1 green power LED
  • Working Principle:
    • The Mark V/VI CPU sends a 12-bit digital value to the board via the backplane bus. The value is latched by a register and presented to a 12-bit D/A converter. For 4–20 mA output, the D/A voltage drives a precision voltage-to-current converter (Howland current pump topology) that sources current into the field loop. The loop current is monitored by a sense resistor, and the feedback is used to maintain accuracy. For 0–10 VDC output, the D/A voltage is buffered by a precision op-amp with rail-to-rail output. The isolation barrier is provided by optical isolators between the backplane logic and the D/A converter, and by the current loop itself for 4–20 mA outputs (the loop is inherently isolated).
  • Installation Requirements:
    • Rack: Mark V or Mark VI I/O rack
    • Wiring for 4–20 mA: Use shielded twisted-pair cable; connect the positive loop wire to the output terminal and the negative loop wire to the return terminal; the field device (valve positioner) completes the loop
    • Wiring for 0–10 : Use shielded twisted-pair; connect the positive output to the field device input and the negative output to the field device common; the field device must have a high-impedance input (10 kΩ minimum)
    • Loop Resistance: For 4–20 mA output, ensure total loop resistance (wire + field device) does not exceed 600 ohms at 24 VDC supply
    • Grounding: Connect the shield to chassis ground at the control system end only
  • Usage Notes:
    • Do not leave a 4–20 mA output loop open; an open loop will cause the output to saturate at 20 mA and trigger a fault
    • Ramp Rate: Always set a ramp rate for control valve applications; a sudden step change can cause water hammer in steam systems or mechanical shock in actuator systems
    • Fail-Safe Selection: For safety-critical valves (e.g., turbine trip valve), always configure fail-to-zero so the valve closes on loss of signal
    • Calibration: Use a precision mA meter or voltmeter to verify each channel at 0%, 25%, 50%, 75%, and 100% of output range; adjust zero and span via the Mark V/VI service software
    • Channel Independence: Each channel has its own D/A converter and output stage; a failure on one channel does not affect the other seven channels

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