GE DS3800XTFT

Key Parameters

Temperature Section:

• Input Channels: 8 differential thermocouple/RTD inputs

• Input Types: Thermocouple (J, K, T, E, R, S, B, N), RTD (Pt100, Ni100), millivolt

• Resolution: 16-bit ADC with ±0.05% accuracy

• Cold-Junction Compensation: Built-in per channel

• Diagnostics: Burnout detection, open-circuit detection, over-range/under-range detection

Frequency Transmitter Section:

• Input Channels: 2 independent frequency input channels

• Input Types: Magnetic pickup, proximity, TTL (5V), or 24V DC (jumper-selectable)

• Maximum Input Frequency: 100 kHz

• Output Types: Analog (4–20mA or 0–10V) or digital (frequency/pulse) output (software-selectable)

• Output Accuracy: ±0.05% of full scale (analog) or ±0.01% (digital)

• Transmitter Function: Converts frequency input to scaled analog signal or retransmits frequency for external systems

• Diagnostics: LED status per channel, input signal loss detection, output fault detection

Common Section:

• Isolation: 1500V RMS channel-to-backplane

• Temp Range: –30°C to +70°C

• Power Supply: +5V, ±15V from VME backplane

• Physical: 6U VME single-slot board

• Key Features: Combined temperature and frequency transmitter, 16-bit ADC, built-in CJC, burnout detection, frequency-to-analog conversion, 100 kHz input

Advantages

• Multi-function capability – the DS3800XTFT combines temperature measurement and frequency-to-analog/digital conversion in a single slot, reducing board count and rack space requirements.

• Built-in cold-junction compensation – on-board CJC for thermocouple inputs eliminates the need for external reference junctions.

• Burnout detection – automatically detects broken thermocouple wires and flags the channel.

• Flexible frequency input – supports magnetic, proximity, TTL, or 24V inputs for speed, flow, or position sensors.

• Scalable output – the General Electric DS3800XTFT converts frequency signals to 4–20mA, 0–10V, or digital pulse outputs for integration with external systems (DCS, SCADA, recorders).

• Diagnostic visibility – per-channel LED status and fault detection simplify troubleshooting.

• Isolation – 1500V RMS isolation protects the backplane from field-side noise and transients.

• Drop-in compatible – works with all Mark IV backplanes and processor configurations.

Applications

• Turbine EGT and speed transmitter – measures exhaust gas temperature (EGT) and converts turbine speed frequency to a 4–20mA signal for external monitoring systems.

• Temperature plus flow transmitter – monitors thermocouple or RTD temperatures while converting flowmeter frequency pulses to analog signals for plant DCS.

• Bearing temperature and speed transmitter – combines bearing RTD inputs with speed pickup frequency-to-analog conversion.

• Signal conditioning for external systems – the DS3800XTFT provides isolated analog outputs for vibration monitors, speed controllers, or plant historians.

• Retrofits – replaces separate temperature boards and frequency transmitters with a single, integrated solution.

vs Competitors & Separate Boards

Selection Tips

• Signal transmission needed – choose the DS3800XTFT when you need both temperature measurement and frequency-to-analog/digital conversion for integration with external systems (DCS, SCADA, recorders).

• Slot-limited installations – ideal for compact systems with limited rack slots where both measurement and transmission are required.

• Application matching – ensure that the 8 temperature channels and 2 frequency transmitter channels meet your system’s requirements.

• Output type selection – the General Electric DS3800XTFT supports 4–20mA, 0–10V, or digital pulse outputs; verify which output type is required by your external system.

• Sensor compatibility – verify that your thermocouple/RTD types and frequency sensors (magnetic, proximity, TTL, 24V) are supported by the DS3800XTFT.

• Spare strategy – keep one DS3800XTFT per 5–8 installed units, especially in systems where it serves multiple critical functions.

• Calibration – periodically verify temperature accuracy using a precision calibrator and frequency-to-output scaling using a signal generator and accurate measurement instrument.

Critical Precautions

• Thermocouple wiring – use the correct extension-grade thermocouple wire (not copper) for temperature inputs to the DS3800XTFT; incorrect wire types introduce cold-junction errors.

• Thermocouple polarity – observe correct polarity when connecting thermocouples; reversed polarity produces inverted readings.

• RTD wiring – use 3-wire or 4-wire RTD connections to cancel lead resistance; 2-wire connections introduce measurement errors.

• CJC location – the DS3800XTFT cold-junction compensation measures the temperature at the terminal block. Ensure the terminal block is not exposed to drafts or radiant heat.

• Frequency input voltage limits – never apply voltage above 30V to the frequency inputs; magnetic pickups can generate high voltages at high speeds – use appropriate attenuation.

• Output load limits – do not exceed the maximum load resistance for 4–20mA outputs (typically 600Ω) or the minimum load resistance for 0–10V outputs (typically 2kΩ) on the General Electric DS3800XTFT.

• Cable shielding – use shielded twisted-pair cables for all thermocouple, RTD, frequency inputs, and analog outputs. Ground the shield only at the DS3800XTFT end to prevent ground loops.

• Ground loops – use single-point grounding for all sensors and outputs connected to the DS3800XTFT to avoid ground-loop noise.

• Output scaling – ensure the scaling parameters (frequency range to output range) are correctly configured in the DS3800XTFT before commissioning.

• Hot-swap – never insert or remove the DS3800XTFT while the rack is powered; this can cause bus errors or component damage.

• ESD handling – always use a grounded wrist strap when handling the DS3800XTFT; CMOS and precision analog components are ESD-sensitive.

• Storage – store spare DS3800XTFT boards in anti-static bags in a dry, temperature-controlled environment.