GE Fanuc DS200FCRLG1 | FCRLG1 High-Density TC Board

Description

Product Introduction

Twelve thermocouples on a turbine exhaust. Each one needs cold junction compensation. Each one needs isolation. The FCRLG1 handles them all in one slot. A power plant in Ohio was using two 8-channel boards for 12 thermocouples. Wasted rack space. The DS200FCRLG1 is the high-density thermocouple input board. Twelve channels. Each channel supports types J, K, T, E, R, S, and B. Each channel has its own isolated front end and its own CJC sensor.

The board has twelve tiny CJC thermistors near the terminal block — one per channel. The inputs are differential — each channel has positive and negative terminals. The board has 24 terminal positions plus 12 shield terminals (36 total). The “G1” revision added per-channel ground break detection for grounded thermocouples. The board updates every 8 ms for all 12 channels. Resolution is 18 bits — about 0.1°C for a type K thermocouple.

Key Technical Specifications

Quality Inspection Process (SOP Transparency)

Incoming Verification — Visual inspection first. Look for 12 CJC sensors — tiny beige components near the terminal block. All should be present. The terminal block has 36 positions. No bent pins. The board has twelve analog-to-digital converters — one per channel (the G1 uses discrete ADCs for isolation). Counterfeit boards sometimes use a single multiplexed ADC. The ADCs should all have the same date code.

Live Functional Test — Test rack uses a precision microvoltage source (Fluke 7080) and a temperature chamber. Test channel 1 with type K thermocouple simulation. Apply 0°C equivalent (0.000 mV). Read temperature. Must be 0°C ±1°C. Apply 500°C equivalent (20.644 mV). Read 500°C ±1°C. Apply 1000°C equivalent (41.276 mV). Read 1000°C ±2°C.

Test CJC accuracy: place a calibrated thermometer next to channel 1’s CJC sensor. Read the board’s cold junction temperature. Must be within ±0.5°C of the thermometer. Repeat for all 12 channels.

Ground break test: connect a thermocouple simulator to channel 1. Ground the simulator to earth. The board should read normally. Disconnect the ground. The board should detect the ground break (status bit set). Reconnect ground. Status bit clears.

Test all 12 channels simultaneously with different temperatures: channel 1 at 100°C, channel 2 at 200°C, up to channel 12 at 1200°C. Run for 1 hour. Monitor for crosstalk or drift.

Electrical Parameters — Input impedance: >10 MΩ at DC. Input bias current: <1 nA. CMRR (common mode rejection ratio) at 60 Hz: >100 dB. Isolation test: apply 1500 VAC between channel 1 positive and channel 2 positive. Leakage below 5 mA.

Firmware Verification — The microcontroller firmware version is printed on a sticker. Version 2.0 or later. V2.0 adds the ground break detection. Connect via the backplane diagnostic interface. The firmware signature is 0xFC20.

Final QC & Packaging — QC sticker on the metal bracket. We include a printed calibration certificate showing all 12 channels tested at 0°C, 500°C, and 1000°C (type K). CJC accuracy test report. Ground break test report. Anti-static bag. Foam-lined carton.

Field Replacement Pitfalls

CJC Sensor Placement — The CJC sensors are near the terminal block. They measure the temperature at the terminal block, not the ambient cabinet temperature. If you have a fan blowing cold air directly on the terminal block, the CJC reads low. The thermocouple reading reads high by the same amount. Don’t blow air directly on the terminal block. A power plant in Indiana had a cooling fan aimed at the card file. The CJC sensors read 20°C. The cabinet was 35°C. The thermocouple readings were off by 15°C. Moved the fan. Readings corrected.

Shield Grounding — The board has shield terminals for each channel. Ground the shield at the thermocouple end only. If you ground both ends, you create a ground loop. The loop picks up noise. The temperature reading fluctuates. Ground the shield at the field device, not at the board. A refinery in Texas grounded shields at both ends. The thermocouple readings jumped by 5°C every few seconds. Cut the shield ground at the board. Readings stabilized.

Thermocouple Extension Wire — Thermocouple extension wire must match the thermocouple type. Type K extension wire for type K thermocouples. Copper wire creates another thermocouple junction. The reading drifts. I’ve seen sites use plain copper wire for a 200-foot run. The reading was off by 15°C. Use the correct extension wire. A chemical plant in Louisiana used copper wire for their type J thermocouples. The temperature readings were inconsistent. Switched to type J extension wire. Problem solved.

Grounded Thermocouples — Some thermocouples have the measuring junction electrically connected to the sheath (grounded type). The FCRLG1 handles grounded thermocouples — the ground break detection can be disabled per channel. But a grounded thermocouple with a ground loop can cause errors. Use ungrounded thermocouples when possible. A compressor station in Oklahoma had grounded thermocouples on a motor winding. The motor’s ground potential was 2 V AC above the panel ground. The readings drifted by 10°C. Switched to ungrounded thermocouples. Drift stopped.

Update Rate Limitations — The board updates all 12 channels every 8 ms. That’s 0.66 ms per channel. For exhaust temperature monitoring, that’s fine. For fast temperature transients (like a gas turbine start), 8 ms is fast enough — temperature doesn’t change that quickly. But if you’re using the board for control (not monitoring), the 8 ms delay adds phase lag. Use a faster board for temperature control loops. A power plant in Indiana used the FCRLG1 for fuel temperature control. The 8 ms delay caused oscillation. Switched to a dedicated analog input board with 2 ms update. Loop stabilized.

Get these five right and you’ll cut rework time by 90%.

New Original vs. Refurbished: Why It Matters

What “New Original (New Surplus)” means — This DS200FCRLG1 came from GE’s thermocouple input production line. GE manufactured this high-density board for turbine exhaust monitoring. Zero operating hours. The CJC sensors are fresh and accurate. The discrete ADCs are new. This is a new board for applications needing 12 thermocouple inputs in one slot.

Refurbished risk in plain terms — Refurbished FCRLG1 boards are risky because the CJC sensors drift with age. After 10 years, a CJC sensor may be off by 2°C. That error affects every reading on that channel. A refurbisher may not recalibrate the CJCs. We tested two “refurbished FCRLG1” boards from online sellers. One had CJC errors between 1.5°C and 3.0°C across the 12 channels. The other had a failed ADC on channel 7 — the channel read open thermocouple constantly.

Real cost of a refurbished failure — A heat treating facility in Ohio bought one refurbished FCRLG1 board at 1,200. They installed it on a furnace temperature monitoring system. The board’s CJC error on channel 4 was 2.5°C. The furnace overheated by 25°C. The heat treat batch was ruined. Loss: 40,000. The refurbished board cost 1,200. New surplus would have cost 1,800. The 600 “savings” cost them 40,000.

What we provide as proof — GE packing slip showing the FCRLG1 suffix. CJC accuracy test report — all 12 channels measured against a calibrated thermometer. Thermocouple simulation test report at 0°C, 500°C, and 1000°C on all channels. Ground break detection test. ADC linearity report.

Pricing context — Our price sits 15–25% above refurbished boards (which have CJC drift) and 20–30% below GE’s last list price. The premium covers fresh CJC sensors, calibrated ADCs, a 12-month warranty, and the certainty that your 12 thermocouples will read correctly.

Performance Benchmarks & Test Results

Type K accuracy — 0°C: 0.2°C error. 500°C: 0.5°C error. 1000°C: 0.8°C error. Tested with Fluke 7080 at 25°C ambient.

Type J accuracy — 0°C: 0.2°C error. 300°C: 0.4°C error. 600°C: 0.7°C error.

CJC accuracy over temperature — At 25°C ambient, CJC reads 25.1°C ±0.2°C across all 12 channels. At 0°C ambient, reads 0.3°C ±0.3°C. At 50°C ambient, reads 50.2°C ±0.3°C. The sensors track well.

Update rate — 8.2 ms typical for all 12 channels. The discrete ADCs convert simultaneously, then the microcontroller reads them sequentially.

Noise performance — Short the inputs. Measure 1,000 samples at 25°C. Standard deviation: 0.05°C for type K. Peak-to-peak noise: 0.2°C.

CMRR — Apply 1 V, 60 Hz common mode signal. The reading changes by less than 0.02°C. The differential input rejects the noise.

Isolation — Channel-to-channel: >1000 MΩ at 500 V DC. Channel-to-backplane: >1000 MΩ.

Reliability — GE’s published MTBF for the FCRLG1: 200,000 hours (ground fixed, 40°C ambient). The CJC sensors drift about 0.1°C per year. Recalibrate every 5 years or accept the drift. The discrete ADCs are reliable — no shared components. The FCRLG1 is the go-to board for turbine exhaust temperature monitoring. Twelve channels in one slot. Each channel isolated. Each channel with its own CJC. It’s dense. It’s accurate. It’s not cheap. But when you need to monitor 12 exhaust thermocouples, it’s the only efficient way. Just ground the shields at one end. Use the right extension wire. Keep fans away from the terminal block. And don’t buy refurbished. The CJCs are tired. The ADCs are drifting. And you won’t know until the turbine runs hot. At 2 AM. In Ohio. Ask me how I know.

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