DS200TCCBG2A | 16-Ch Thermocouple Board

Description

Product Introduction (Anti-Template)

When you need to monitor 12-16 thermocouples in a single rack slot, the DS200TCCBG2A is your only option. This board packs 16 thermocouple inputs into the same 6U footprint as the 8-channel TCCBG1 series—double the capacity at a fraction of the cost per channel. The trade-off? Resolution drops to 14-bit (versus 16-bit), accuracy is ±0.7°C (versus ±0.5°C), and instead of per-channel CJC, the board uses a shared CJC reference for all 16 channels.

The ‘2’ in the part number tells you this is the high-density variant in the TCCBG family. It’s built for applications where channel count matters more than absolute accuracy—monitoring multiple bearing temperatures, general-purpose temperature monitoring on large turbine skids, or applications where you have many thermocouples but don’t need the tightest tolerance. Compared to the TCCBG1A (8 channels, 16-bit, per-channel CJC, ±0.5°C), the TCCBG2A gives you twice the channels with a shared CJC reference and lower accuracy. If you have 10-16 thermocouples and you’re running out of rack slots, this board solves the problem—but be aware of the shared CJC limitation.

Key Technical Specifications

Compatible Replacement Models

Replacement options depend on your channel count and accuracy requirements.

✅ Drop-in Replacement: The DS200TCCBG2 (no ‘A’ suffix) is a direct electrical drop-in—same pinout, same 16 channels, same shared CJC. The ‘A’ revision improved the accuracy from ±1.0°C to ±0.7°C and added a better reference. If you find the base model, it works—just with wider tolerances.

⚠️ Software Compatible: The DS200TCCBG1A (8 channels, 16-bit, per-channel CJC) fits the rack but is not a drop-in replacement. If you swap a TCCBG2A for a TCCBG1A, you’ll lose channels 9-16 (they’ll read invalid). You would need to re-wire your termination panel to use the TCCBG1A’s 8 channels. This is a downgrade, not an upgrade.

⚠️ Software Compatible: The DS200TCCBG1B (8 channels, 16-bit, per-channel CJC, filtering) is a higher-precision alternative—but you lose half your channels.

❌ Hardware Incompatible: Any general-purpose analog board (TCCAG1 series) or discrete I/O board (TCCX series) uses different backplane pins—not suitable for thermocouple inputs.

Frequently Asked Questions (FAQ)

What’s the difference between the TCCBG2A and the TCCBG1A?

The TCCBG1A is a precision board: 8 channels, 16-bit resolution, per-channel CJC, ±0.5°C accuracy. The TCCBG2A is a high-density board: 16 channels, 14-bit resolution, shared CJC, ±0.7°C accuracy. The trade-off is clear: channel count vs. precision and CJC accuracy. The TCCBG2A is for applications with many thermocouples that don’t require the highest accuracy—general monitoring vs. critical control loops.

Why doesn’t this board have per-channel CJC?

Board space and cost. Sixteen channels with per-channel CJC would require 16 separate CJC sensors and associated circuitry, which wouldn’t fit in a 6U VME board without significant redesign. The TCCBG2A uses a single CJC sensor for all 16 channels, assuming the termination board is isothermal (same temperature across all terminals). This is acceptable for many monitoring applications, but it means that if your termination board has temperature gradients (e.g., one side is warmer than the other), you’ll see errors on channels furthest from the CJC sensor.

How does the shared CJC affect accuracy?

The shared CJC sensor measures the temperature at one point on the termination board. The TCCBG2A assumes the entire termination board is at the same temperature. In practice, there’s typically a 1-2°C gradient across the board. This means channels near the CJC sensor will be accurate, while channels further away may have an error of 1-2°C. If your application requires better than ±1°C accuracy, the TCCBG2A may not be suitable. The per-channel CJC of the TCCBG1 series eliminates this error source.

Can I use this board with a Mark VIe controller?

No—the TCCBG2A uses the older Mark VI backplane pinout. Mark VIe uses a different assignment and typically uses the IS200TCCBG2A for high-density thermocouple inputs. Use the Mark VIe-specific board for new installations.

How do I test this board before installation?

Testing the TCCBG2A requires checking all 16 channels and the shared CJC:

1. Visual inspection: Check for burnt or discolored components. The high-density board has more components in the same space—look for cracked solder joints around the multiplexer.
2. Power-up test: Install the board in a test rack and apply 24 VDC. The board’s status LED (green) should illuminate within 2 seconds.
3. Firmware check: Read the firmware version via ToolboxST—should be 2.0 or later.
4. CJC test: With no thermocouples connected, read the CJC temperature. It should match ambient within ±0.5°C.
5. Input test – accuracy: Apply a precision 10.00mV DC (equivalent to about 250°C on Type K) to channel 1. The read value should match the expected temperature ±0.7°C. Repeat for channels 1-16.
6. Channel crosstalk: Apply a full-scale signal to channel 1 and read channel 2. The crosstalk should be less than 0.2% of full scale (60dB CMRR).
7. CJC gradient test: If you can create a temperature gradient on the termination board (e.g., warm one side with a heat gun), measure the temperature difference between the CJC sensor location and the far end of the board. The error on the far channels will be roughly the temperature gradient—this is the shared CJC limitation.

What’s the most common failure on this board?

Two issues specific to the high-density thermocouple design:

1. Multiplexer failure. The TCCBG2A uses a multiplexer to switch between channels—only one channel is digitized at a time. If the multiplexer fails, you’ll get stable readings on some channels and erratic readings on others. The symptom is “jumping” values on a specific channel while others are stable.
2. Shared CJC sensor drift. The single CJC sensor can drift over time, causing a consistent offset on all channels. The symptom: all channels read 2-5°C high or low. The fix: recalibrate or replace the termination board (the CJC sensor is on the termination board, not the TCCBG2A).

If I’m using this board in a SIL-rated safety application, what’s the recommended maintenance interval?

The shared CJC makes this board unsuitable for SIL-3 applications. For SIL-2, we recommend:

• Visual inspection: Every 6 months
• Power-up test: Every 12 months
• Input accuracy check: Every 12 months (0.7°C spec)
• CJC check: Every 12 months (verify CJC matches ambient)
• CJC gradient check: Every 12 months (measure temperature across termination board—should be within ±1°C)
• Full calibration: Every 5 years

What’s the lead time for a replacement TCCBG2A?

These boards are less common than the TCCBG1A:

• New surplus: 2-4 weeks. The high-density board is less common but still available.
• Refurbished: 1-2 weeks. Ensure the refurbisher tests all 16 channels—some only test a subset.
• Used/as-is: Available, but the multiplexer is a wear item—used boards may have intermittent channel failures.

Is there a direct Mark VIe equivalent?

Yes—the IS200TCCBG2A (Mark VIe version). The backplane pinout is different, and the Mark VIe board may have a different CJC scheme (some variants use per-channel CJC at higher cost). If you’re migrating to Mark VIe, plan to replace all high-density thermocouple boards as part of the rack conversion.

Which termination board should I use with the TCCBG2A?

The TCCBG2A is designed to interface with the DS200TBCBG2A (if available) or the DS200TBCBG1A termination board. The termination board provides the single shared CJC sensor and the terminal connections. For best accuracy with the shared CJC design, use a termination board that is as isothermal as possible—avoid mounting it near heat sources or drafty areas. The termination board’s CJC sensor location determines the reference temperature for all 16 channels.

What’s the update rate for all 16 channels?

The TCCBG2A scans channels sequentially with a 50ms total update time—each channel updates every 50ms, but they’re not sampled simultaneously. Channel 1 updates at t=0ms, channel 2 at t=3.125ms, etc. If you need simultaneous sampling, you need a TCCBG1 series board. The sequential sampling is acceptable for most temperature monitoring applications.

What’s the maximum cable length for thermocouples on this board?

GE recommends a maximum of 200 feet (60 meters) for the TCCBG2A—shorter than the TCCBG1 series (300 feet) due to the lower input impedance (>1MΩ vs. >10MΩ). The lower impedance means the board is more susceptible to lead wire resistance errors. For critical thermocouples, keep cable runs as short as possible and use the correct thermocouple extension wire.

What’s the correct thermocouple wire type for this board?

The TCCBG2A supports J, K, T, E, and N thermocouples—it does NOT support R, S, or B types (the high-temperature thermocouples). If you need R, S, or B thermocouples, you’ll need the TCCBG1 series. The thermocouple type is configured in software (ToolboxST) per channel. For best accuracy, use premium-grade thermocouple wire—the 0.7°C accuracy is wasted on standard-grade wire.

What’s the difference between the TCCBG2A and the TCCBG2 (base model)?

The base TCCBG2 (no ‘A’ suffix) has ±1.0°C accuracy and a less stable reference. The TCCBG2A improves accuracy to ±0.7°C and uses a better voltage reference (±100ppm/°C vs. ±150ppm/°C). If you find the base model, it works—but the ‘A’ revision is worth the small premium for the improved accuracy.

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