Quick Sizing & Sourcing Snapshot
- Manufacturer: GE (General Electric)
- Part Number: IS200STTCH2A (Also referenced as )
- System Platform: Mark VI / Mark VIe (Speedtronic)
- Hardware Type: Simplex Thermocouple Input Terminal Board (STTC)
- Architectural Role: Provides the passive field-wiring interface for 24 thermocouple sensors, handling Cold Junction Compensation (CJC) before signal hand-off to the STCC logic board or PAICH1A I/O pack.
- Key Specifications: 24 TC Channels, On-board CJC Sensor, DIN-Rail Mount, Simplex Architecture.
System Architecture & Operational Principle
The is a passive terminal board operating at Level 1 (Field Termination) in both Mark VI (VME) and Mark VIe (Distributed) architectures. It is the Simplex variant (denoted by ‘STTC’), meaning it interfaces with a single processing path—typically a STCC logic board in Mark VI or a PAICH1A Analog Input pack in Mark VIe.
Physically, it mounts on a 35mm DIN rail via a metal carrier and plastic insulator. Field-side thermocouple wires (Exhaust TTs, Bearing TTs, Flame Scanners) land on its 48-position screw terminal block (split into two rows of 24). The board houses the Cold Junction Compensation (CJC) sensor (usually a thermistor/semiconductor) positioned right at the screw clamps to read ambient temperature accurately. It connects to the active processor via a 37-pin D-sub connector (JH1). Upstream, the processor digitizes the millivolt signals, applies the CJC offset, and converts to engineering units (Deg F/C) for the controller. Unlike the TMR version (TCTB), this board has no voting logic; it’s a straight 1:1 signal path for auxiliary or non-critical temperature loops where triple redundancy isn’t justified.
Core Technical Specifications
- Channel Density: 24 Isolated Thermocouple Inputs
- Supported Types: J, K, T, E, R, S, B (Software Selectable per channel)
- Signal Range: -8 mV to +45 mV (Typical TC spans)
- CJC Accuracy: ±0.5°C to ±1.0°C (On-board sensor at terminal block)
- Field Interface: 48-Screw Terminals (Accept #12 – #24 AWG, Pluggable or Fixed)
- Processor I/F: 1x 37-pin D-Sub (JH1 to STCC / PAICH1A)
- Isolation: Channel-to-Channel (Via Optos on Pack), Galvanic on Board
- Filtering: RC Networks (50/60Hz notch for noise rejection)
- Power: Passive (Sensed voltage from TC; Logic power from Pack via D-Sub)
- Mounting: 35mm DIN Rail (TS-35) via Metal Carrier + Insulating Shim
- Environmental: -20°C to +65°C (Operational), Conformal Coated
High-Frequency Troubleshooting FAQ
Q: ToolboxST shows “Input Failure” or “Open Circuit” on a channel, but the TC ohms out good at the field.
A: Check Screw Terminal Tension first. Pop the TC wire; if strands are flattened or the screw spins freely, the clamp is compromised. These use saddle clamps; over-torquing cracks the plastic, causing intermittent contact. Also, verify the CJC Jumper (if present on specific sub-revs) is set to “Internal” (On-board sensor). If set to “External” and no probe is attached, the system will flag every channel as open/failed.
A: No. The ‘STTC’ denotes Simplex. It has one 37-pin connector (JH1). For TMR, you need IS200TCTBH2A (Triple connectors: JR1, JS1, JT1). If you force a Simplex board into a TMR software config, the controller will fault expecting three votes and only getting one signal path.
Q: Temp readings are rock solid but off by a constant +15°F across all 24 channels.
A: Your CJC Reference is off. The board senses temp at the PCB. If the board is mounted in a hot spot (near exhaust fans), the PCB is hotter than the field wire junction. In ToolboxST -> I/O Config -> Terminal Board, apply a CJC Offset (e.g., -0.8mV for ~15°F error at Type K) to shift the baseline. Alternatively, relocate the DIN rail mount to a cooler zone of the cabinet.
Please note: The listed price is not the actual final price. It is for reference only and is subject to appropriate negotiation based on current market conditions, quantity, and availability.
