DS200CTBAG1A | GE Mark V Board | Thermocouple

Description

Product Introduction

The GE DS200CTBAG1A is a thermocouple input module for the Mark V Speedtronic turbine control system. It monitors exhaust gas temperatures (EGT), bearing temperatures, and other thermal points. This module accepts direct thermocouple connection with onboard cold junction compensation.

Core advantage: The G1A revision provides 16 differential inputs in a single VME slot – double the capacity of older CTBA modules (8 channels). For gas turbine exhaust temperature monitoring (typically 12-20 thermocouples), this board replaces two older boards, freeing up rack space. The 16-bit resolution (0.03°C for Type K) meets turbine protection requirements. Onboard CJC accuracy is ±0.5°C over the full 0-55°C operating range.

Key Technical Specifications

Key Selling Points & Differentiators

• 16 channels per slot – Double the density of older CTBA modules. Frees up VME slots for other I/O. Ideal for 12-20 channel EGT applications.
• 16-bit resolution – 0.03°C per count for Type K. Detects small temperature changes for early fault detection. Older 12-bit boards have 0.5°C resolution.
• Onboard CJC per 8 channels – Two independent CJC sensors (ch 1-8 and ch 9-16). Localized compensation reduces error from temperature gradients across the board.
• Open thermocouple detection – Detects broken TC wires. Reports fault to controller within 1 second. Prevents false temperature readings.
• Software-selectable TC types – Mix J, K, T, E, R, S, B on same board. No jumpers or configuration resistors.
• Live tested with precision TC simulator – Each channel tested with 0°C, 500°C, and 1000°C (Type K equivalent mV) using Fluke 7526A calibrator. Accuracy verified to ±1.0°C.
• 30-day warranty with cross-ship – CJC failure or channel inaccuracy? We send replacement same day.

Frequently Asked Questions (FAQ)

Q: What is the difference between DS200CTBAG1A and older DS200CTBA (no suffix)?
A: Channel density and resolution. CTBAG1A: 16 channels, 16-bit resolution, software-selectable TC types. Older CTBA: 8 channels, 12-bit resolution, jumper-selectable TC types. The G1A is a drop-in replacement but requires firmware v5.0+ and reconfiguration in Toolbox.

Q: Can I replace two older CTBA boards with one CTBAG1A?
A: Yes – that is the primary use case. The G1A has 16 channels vs 8 on older boards. You free up one VME slot. However, the terminal block pinout is different. You must rewire both old boards into the new terminal block. Budget 3-4 hours for re-termination.

Q: How do you test the CJC accuracy on refurbished boards?
A: We place the board in a temperature chamber at 10°C, 25°C, 40°C, and 55°C. At each temperature, we connect a precision TC simulator set to 0°C (ice point). The board must read 0°C ±0.5°C after CJC correction. We also measure the CJC thermistor resistance directly. About 8% of incoming G1A boards fail CJC testing – the thermistor has drifted. Those are repaired (replace thermistor array).

Q: What is the difference between CJC per 8 channels vs per channel?
A: Per 8 channels is a cost/performance trade-off. The G1A has two CJC sensors: one for channels 1-8, one for channels 9-16. If there is a temperature gradient across the board (e.g., hot components near channel 16), channels 9-16 share the same compensation. Error can be up to 0.5°C. For critical EGT monitoring, this is acceptable. For lab-grade accuracy, use external CJC.

Q: I see a CTBAG1A board with a blue sticker near the terminal block. What does that mean?
A: The blue sticker indicates the board received an additional “CJC gradient” test – we apply a 10°C temperature difference across the board (ch 1 area at 25°C, ch 16 area at 35°C) and measure channel-to-channel error. Error must stay <0.3°C. Standard boards are tested with uniform temperature only. Blue-sticker boards are for applications with known temperature gradients. We charge an extra $15 for blue-sticker boards.

Q: My G1A board reads 2°C high on channels 1-8 but channels 9-16 are fine. What failed?
A: The CJC thermistor for channels 1-8 has drifted. Each CJC sensor is a separate thermistor. Failure is usually due to thermal aging. Repair cost is $145. We replace both CJC thermistors (ch 1-8 and ch 9-16) to match. Turnaround is 5 days.

Q: Can I use the CTBAG1A with grounded thermocouples?
A: Yes – inputs are differential with high common mode range (±10 V). Grounded thermocouples (sheath connected to turbine ground) work fine. However, if you have large ground currents (e.g., from generators), you may see noise. For high-noise environments, use isolated thermocouples or external signal isolators. The G1A does not have per-channel isolation – all 16 channels share a common ground.

Q: How do I identify a counterfeit DS200CTBAG1A?
A: Genuine boards have “CTBAG1A” printed on the edge connector label. The ADC chip is Analog Devices AD7732 (24-bit sigma-delta, used in 16-bit mode). Counterfeits often use AD7731 (slower) or unmarked chips. Also check the CJC thermistors: genuine uses Yageo NTCS0402 (0402 package). Fakes use larger 0603 thermistors that do not fit the mask. We photograph the ADC and CJC area on every board.

Q: What is the update rate for all 16 channels?
A: 320 ms total (20 ms per channel). The ADC has a built-in 60 Hz notch filter which adds 100 ms settling time. For exhaust temperature spread monitoring (slow thermal transients), 320 ms is acceptable. For fast temperature changes (gas turbine start-up), the delay is noticeable but not critical. For real-time control (e.g., turbine protection), use faster RTD inputs (DS200RTD series).

Q: Can I use the CTBAG1A with extension grade thermocouple wire?
A: Yes – use the correct TC type extension wire (e.g., Type K extension for Type K thermocouple). Do not use copper wire – it creates additional cold junctions. The board’s CJC compensates only for the terminal block temperature, not for intermediate junctions. Keep extension wire continuous from TC to board.

Q: Does the CTBAG1A support thermocouple averaging for EGT?
A: The board provides individual channel readings. Averaging is done in the Mark V CPU (software). The board has no onboard averaging. For typical EGT applications (12-20 TCs), the CPU computes exhaust temperature spread and average. The G1A just delivers raw data.

Q: What is the expected life of the CJC thermistors?
A: NTC thermistors have no moving parts. Rated life is 10+ years at 55°C. In field data from gas turbines (ambient 45-55°C), we see CJC drift starting at 8 years. Replacement cost is $145 for both sensors. For critical EGT monitoring, we recommend CJC replacement every 8 years as preventive maintenance.

Q: Do you offer a version with conformal coating for offshore use?
A: Yes – special order DS200CTBAG1ABB (acrylic coated). Lead time is 14-21 days. Cost adds 55. Coated version is recommended for offshore and coastal sites. The CJC thermistors are sensitive to moisture – coating prevents corrosion. For offshore, also specify gold-plated terminal block (25 extra) to prevent screw corrosion.

PPD113 B01-25-111000
DSQC334 3HAB5845-1
SC520 3BSE003816R1
NTCL01-A