The IS200DTCIH1A is a Simplex Contact Input Terminal Board with Group Isolation designed by General Electric (GE) for its Mark VI™ Control System. This board is the standard version within the DTCI series, featuring a compact design specifically for DIN-rail mounting. It provides the control system with 24 dry contact input channels for signal acquisition and processing. The IS200DTCIH1A board works in conjunction with the VCCC or VCRC processor board, connecting via a single cable to acquire 24 contact input signals.
The design of the IS200DTCIH1A board shows industrial field space limitations and application requirements. Its compact dimensions (8.6 cm wide × 16.2 cm high) allow multiple boards to be stacked vertically on a DIN rail, significantly saving control cabinet space. The board features a permanently mounted EuroBlock type terminal block with 60 terminals for connecting field contact input signals. An onboard ID chip identifies the board to the I/O pack for system diagnostic purposes.
Key features of the IS200DTCIH1A include:
Compact Design: Suitable for DIN-rail mounting, can be stacked vertically to save cabinet space.
24 Contact Inputs: Provides 24 dry contact input channels with a nominal excitation voltage of 24 V dc.
Group Isolation Design: Input channels feature group isolation, enhancing system noise immunity.
Coordination with VCCC/VCRC: Connects to VCCC or VCRC processor boards via a single cable. Each processor board can support two DTCI boards, providing 48 contact inputs total.
Wide Excitation Voltage Range: Supports an excitation voltage range of 18 to 32 V dc, adapting to different field power conditions.
Input Filtering: Each input channel features a hardware filter at the signal entry point to suppress high-frequency noise and surges.
Fault Detection: Can detect loss of excitation voltage, input response faults, and disconnected cables.
ID Chip Identification: Onboard ID chip read by the I/O pack ensures hardware compatibility.
Jumperless Design: The board has no configurable jumpers; all functions are fixed, simplifying field maintenance.
The board operates within a temperature range of 0 to 60°C, suitable for industrial control cabinet environments. It is important to note that the DTCI is only available in a simplex version, does not support TMR applications, and is not compatible with the PDIA I/O pack.
II. Main Functions
The primary functions of the IS200DTCIH1A include, but are not limited to, the following:
1. Contact Input Acquisition
The IS200DTCIH1A board provides 24 dry contact input channels for acquiring the on/off status of field devices such as switches, relay contacts, and pushbuttons. Each input channel uses a nominal 24 V dc excitation voltage, with an allowable range of 18 to 32 V dc, adapting to different field power conditions. The input threshold voltage is 50% of the excitation voltage, ensuring reliable switching status detection.
2. Input Current Characteristics
Input current differs between channels:
First 21 Channels: Each channel draws 2.5 mA nominal current (corresponding to 50 kΩ input impedance).
Channels 22 through 24: Each channel draws 10 mA nominal current (corresponding to 12.5 kΩ input impedance).
3. Noise Suppression and Filtering
Each input channel features a hardware filter at the signal entry point with the following functions:
High-Frequency Noise Suppression: Filters high-frequency interference components from field signals.
Surge Suppression: Absorbs and attenuates transient overvoltages, protecting downstream circuits.
4 ms Filter Time: Ensures input signal stability and noise immunity.
4. Coordination with VCCC/VCRC
The IS200DTCIH1A connects to a VCCC or VCRC processor board via a single cable. Each processor board can support two DTCI boards, providing a total of 48 contact inputs. The VCCC/VCRC board receives the input signals through optical isolators and transmits them via the VME backplane to the VCMI board, and finally to the controller.
5. Group Isolation Design
The IS200DTCIH1A features a group isolation design, enhancing system noise immunity and reliability. Input channels are isolated in groups, effectively preventing common-mode interference and ground loop issues.
6. ID Chip Identification
The board features a read-only ID chip storing the board's serial number, type, revision number, and connector location information. The I/O pack reads this information during initialization. If a mismatch is encountered, a hardware incompatibility fault is generated, preventing system problems caused by incorrect configuration.
7. Fault Detection
The IS200DTCIH1A supports multiple fault detection functions:
Excitation Voltage Monitoring: Monitors the contact input excitation voltage. If the voltage drops below 40% of the nominal value, a diagnostic alarm is set and latched.
Input Response Test: In test mode, non-responding input channels can be detected.
Cable Disconnect Detection: Detects if the connection cable to the processor board is disconnected.
III. System Applications
1. Application in Mark VI Control System
The IS200DTCIH1A is a compact terminal board for contact input signal acquisition within the Mark VI control system. Its roles within the system include:
Switch Status Monitoring: Acquires the status of various field switch devices, such as breaker positions, disconnect switch states, and pushbutton states.
Alarm Signal Input: Receives alarm signals from field devices, such as temperature switches, pressure switches, and level switches.
Equipment Status Feedback: Acquires operating status feedback from devices like motor starters and valve actuators.
Remote I/O Expansion: Flexibly expands the system's contact input capacity by stacking multiple DTCI boards.
2. Differences from TBCI
The main differences between DTCI and TBCI are the excitation voltage level and size:
| Feature | DTCI | TBCI |
| Excitation Voltage | 24 V dc | Multiple options (24/48/125 V dc, etc.) |
| Size | Compact (8.6 cm wide) | Standard (17.8 cm wide) |
| Mounting Method | DIN-rail | Panel mount |
| Number of Channels | 24 | 24 |
| Stackability | Can be stacked vertically | Not stackable |
3. Typical Application Scenarios
Gas Turbine Control: Acquires switch status and alarm signals from various auxiliary devices.
Steam Turbine Control: Monitors valve positions, oil system status, etc.
Generator Excitation Systems: Acquires various status signals within the excitation system.
Auxiliary System Control: Acquires discrete signals in auxiliary systems like oil systems and cooling water systems.
Remote I/O Stations: Serves as a contact input interface for remote I/O stations.
IV. Detailed Interface Description
1. Terminal Block
The IS200DTCIH1A features a permanently mounted 60-terminal EuroBlock type terminal block for connecting all contact input signals. Terminal assignments are as follows:
Terminals 1-54: 24 contact inputs (each input uses 2 terminals: signal high and signal low).
Terminals 55-56: SCOM (shield common), must be connected to ground with the shortest possible wire.
Terminals 57-62: 6 screw terminals for connecting the 24 V dc excitation power.
2. Connector
The board connects to the VCCC or VCRC processor board via a single cable connector. This cable transmits the acquired contact input signals to the processor board for optical isolation and processing.
3. Grounding Requirements
Important: SCOM (terminals 55 and 56) must be connected to ground with the shortest possible wire to ensure shielding effectiveness and system stability. The board has no dedicated shield terminal strip, making this ground connection particularly critical.
4. Excitation Power Connection
The 24 V dc excitation power is connected to the board via terminals 57-62. These terminals are paralleled, allowing any of them to be used for convenient wiring. The excitation power supply is floating, with an allowable range of 18 to 32 V dc.
V. Diagnostics and Maintenance
1. Diagnostic Functions
The IS200DTCIH1A provides the following diagnostic functions via the I/O pack:
| Diagnostic Item | Description |
| Excitation Voltage Monitoring | Monitors the contact input excitation voltage. If the voltage drops below 40% of the nominal value, a diagnostic alarm is set and latched. All input channels are forced to the open contact (fail-safe) state. |
| Input Response Test | In test mode, non-responding input channels are detected. Faulty channels are forced to the fail-safe state. |
| TMR Voting Mismatch | In TMR systems (when used with a TMR configuration), if the input from this board does not match the voted median value from all three boards, a fault is created. |
| ID Chip Verification | Reads the onboard ID chip and compares it with the configuration. A mismatch generates a hardware incompatibility fault. |
2. Fail-Safe State
When an undervoltage excitation condition or an input channel fault is detected, the affected input channels are forced to the open contact state (fail-safe state), ensuring the system can respond safely under fault conditions.
3. Common Troubleshooting
| Fault Symptom | Possible Cause | Troubleshooting Suggestions |
| All inputs not responding | Excitation power failure, disconnected cable | Check 24 V power supply, check connection cable |
| Single input not responding | Field wiring error, contact fault | Check wiring for that channel, test field contact |
| Intermittent input false triggering | Poor grounding, interference | Check SCOM grounding, check shielding |
| Frequent diagnostic alarms | Unstable excitation voltage | Check 24 V power supply stability |
| Hardware incompatibility fault | ID chip information mismatch | Verify correct board model, contact GE technical support |
4. Maintenance Recommendations
Periodic Inspection: Check terminal blocks for looseness and wires for oxidation.
Cleaning: Regularly clean the board to prevent dust accumulation affecting heat dissipation and insulation.
ESD Protection: Wear a grounding strap when handling the board and store it in anti-static bags.
Spare Parts Management: Maintain a spare IS200DTCIH1A board to reduce downtime in case of failure.
VI. Installation and Configuration
1. Installation Steps
Mount DIN Rail Holder: Install the plastic holder onto the DIN rail.
Install Board: Slide the DTCI board into the holder until it snaps into place.
Connect Wires: Connect field contact input wires to the terminal block. Use #18 AWG wire.
Ground Connection: Connect terminals 55 and 56 (SCOM) to ground using the shortest possible wire.
Connect Excitation Power: Connect the 24 V dc excitation power to any one or more of terminals 57-62.
Connect Cable: Connect the cable to the board and to the VCCC/VCRC processor board.
Verify Installation: Confirm all connections are secure.
2. Multi-Board Stacking
When multiple DTCI boards are required, they can be stacked vertically on the DIN rail. Each board connects independently to the VCCC/VCRC processor board (each processor board can support up to two DTCI boards). When stacking, ensure adequate spacing between boards for heat dissipation and wiring access.
3. Wiring Precautions
Use appropriately sized wire (#18 AWG recommended).
The SCOM connection should be as short as possible and connected directly to ground.
Choose an appropriate wire gauge for the excitation power leads to ensure they can carry the total current of all channels.
It is recommended to use shielded cable for field contact connections, with the shield grounded at a single point at either the source or destination.
