What is the IS200STCIH2A?

The IS200STCIH2A is a simplex contact input terminal board developed by GE under the Mark VIe series. It functions as a 24-channel dry contact input interface that mounts on DIN rails or flat surfaces, providing the physical termination and signal conditioning layer between field contact devices and the PDIA I/O processor.

What is the function of the IS200STCIH2A?

The board's primary function is to accept, condition, and transmit discrete contact input signals to the Mark VIe controller. It provides excitation voltage distribution, input threshold detection at 50% of excitation voltage, hardware filtering with 4 ms delay, and surge/noise suppression. The conditioned signals are routed through a 37-pin D-type connector to the PDIA I/O pack, which converts them to digital data and transmits them via Ethernet to the controller.

Why choose the IS200STCIH2A?

The IS200STCIH2A offers proven compatibility with GE's Mark VIe and Mark VIeS control platforms, supporting hazardous location certifications when paired with approved I/O packs. Its 24-channel density reduces cabinet space requirements, while the multi-voltage excitation capability (24/48/125 VDC) accommodates diverse field devices. The built-in noise suppression and diagnostic features enhance system reliability, and the DIN-rail mounting simplifies installation and maintenance in turbine control and power generation applications.

Key Features

Channel Capacity: Accommodates 24 discrete contact inputs on a single board.

System Redundancy: Supports simplex (single) configurations only.

Excitation Voltage Support: Accepts nominal 24 V DC, 48 V DC, and 125 V DC excitation from external sources.

I/O Pack Compatibility: Plugs directly into a D-type connector to interface with a PAIC or compatible discrete I/O pack, routing data via Ethernet to the main controller.

Fault Detection: Monitors and flags excitation voltage loss at the contact inputs and identifies any contact input failing to respond during system test modes.

Wiring Interface: Features a right-angle header supporting multiple styles of pluggable terminal blocks for a total of 52 terminals, typically utilizing #18 AWG wiring.

Noise Suppression: Built-in signal filters protect internal circuitry against surges and high-frequency field noise.

Hardware Filter: Features an onboard 4 ms hardware filter for input signal stabilization.

Parameter specifications

The difference between IS200STCIH2AED and IS200STCIH2A

Frequently Asked Questions

What I/O packs are approved for use with the IS200STCIH2A in hazardous locations?

The IS200STCIH2A is approved for use with Mark VIe discrete I/O packs IS220PDIAH1A and IS220PDIAH1B. The coated variant IS221PDIAH1B requires the conformal-coated terminal board IS201STCIH2A. Safety-rated Mark VIeS systems use the IS220YDIAS1A or ISx2yYDIAS1B packs with the corresponding IS200STCIS2A or ISx0ySTCIS2A terminal boards.

Why do channels 22–24 on the IS200STCIH2A draw 10 mA while channels 1–21 draw only 2.5 mA?

The higher current allocation on the final three channels supports applications requiring greater drive capability, such as direct solenoid valve interfacing or high-impedance contact loops. Engineers should verify that the external excitation supply and field device ratings accommodate this differential loading, particularly in 24 Vdc systems where the aggregate current approaches the 0.5 A resettable fuse limit.

Can the IS200STCIH2A be used in a TMR (triple modular redundant) Mark VIe system?

No. The IS200STCIH2A is restricted to simplex configurations. TMR discrete input applications require the IS200TBCIH4C terminal board combined with three PDIA I/O packs, as specified in the Mark VIe system hardware manual. Attempting to deploy the STCIH2A in a voted architecture will result in a configuration mismatch and loss of redundancy.

What are the recommended practices for troubleshooting 125 Vdc ground faults on installations using the IS200STCIH2A?

Field experience indicates that ground faults on 125 Vdc excitation circuits often originate from environmental degradation rather than board-level defects. Maintenance teams should isolate outgoing branches sequentially using a 250 V or 500 V insulation resistance tester, identifying circuits below 0.5 MΩ as degraded. Inspection should focus on outdoor junction boxes, cable gland plates, and low points in cable trays where moisture or conductive dust accumulation creates leakage paths. Surge protection devices should be verified against IEC 61000 compliance standards, particularly in coastal or lightning-prone regions.

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