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Product Overview
The ABB TB851 (3BSC950194R1) is a CEX-Bus Terminator module designed to ensure reliable communication across the CEX-Bus (Controller Extension Bus) in ABB AC 800M and 800xA distributed control systems. It serves as a termination point at the end of the CEX-Bus communication line, preventing signal reflection and communication errors in high-speed data transmission between the controller and I/O modules.
The TB851 is compact and rugged, offering plug-and-play connectivity within AC 800M system configurations. Its function is fundamental to maintaining signal integrity, especially in environments where electromagnetic interference (EMI) or extended wiring distances can compromise communication reliability.
Although a passive component in function, the TB851 plays a critical role in ensuring the operational stability and data accuracy of ABB’s industrial automation systems.
Product Specifications
| Parameter | Details |
|---|---|
| Model Number | TB851 |
| Part Number | 3BSC950194R1 |
| Product Type | CEX-Bus Terminator |
| Function | Terminates CEX-Bus communication line to prevent signal reflection |
| Bus Compatibility | CEX-Bus (Controller Extension Bus) |
| Voltage Rating | Passive unit (does not require power) |
| Mounting Type | DIN rail or panel mount (S800 I/O mechanics) |
| Material | Industrial-grade plastic housing |
| Environmental Compliance | RoHS compliant, WEEE directive |
| Operating Temperature | 0°C to +55°C |
| Storage Temperature | -40°C to +70°C |
| Humidity | 5%–95% non-condensing |
| Dimensions (H × W × D) | 55 x 16 x 45mm |
| Weight | 0.04 kg |
| System Compatibility | AC 800M, 800xA DCS |
| Certifications | CE, RoHS, UL |
| Manufacturer | ABB Group |
Applications
The TB851 CEX-Bus Terminator is used in a range of industries where ABB’s AC 800M controllers and S800 I/O systems are deployed. It ensures reliable signal transmission and data communication, especially in large or high-speed network layouts.
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Power Generation: Guarantees stable communication between turbine controllers and field I/O modules.
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Petrochemical and Oil & Gas: Critical for maintaining error-free data in hazardous, high-interference environments.
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Water and Wastewater Treatment: Supports signal integrity in geographically dispersed control systems.
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Manufacturing Automation: Ensures reliable real-time data transmission in process-intensive operations.
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Mining and Metals: Resilient performance under extreme temperature and vibration conditions.
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Pulp and Paper: Facilitates continuous communication across long DCS networks in large plants.
In all cases, it prevents the signal degradation caused by improper or missing termination on the CEX-Bus line.
Product Advantages
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Essential Communication Stability: Terminates the CEX-Bus to prevent electrical reflection and data corruption.
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Compact Design: Minimal footprint allows for easy installation in tight control cabinets.
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Maintenance-Free: No moving parts or power requirements — highly reliable over long service life.
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Easy Integration: Installs quickly into standard S800 I/O racks or DIN rail configurations.
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Wide System Compatibility: Fully compatible with ABB’s AC 800M, PM861, PM864, and related controllers.
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Industrial Durability: Operates efficiently in harsh environments with high EMI or temperature variation.
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Lightweight and Robust: Durable housing protects internal circuitry while keeping weight low.
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Compliant with Global Standards: CE, RoHS, and UL compliant for international industrial use.
Frequently Asked Questions (FAQ)
1. What is the function of the TB851?
It terminates the Controller Extension Bus (CEX-Bus) to prevent signal reflection and communication errors.
2. Is the TB851 required in every system?
Yes, at least one terminator is required at the end of every CEX-Bus to maintain communication integrity.
3. Does the TB851 require a power supply?
No, it is a passive component and does not require external power.
4. How do I install the TB851?
It can be mounted directly to a DIN rail or inserted into the terminal section of an S800 I/O system.
5. What happens if I do not use the TB851?
Omitting the terminator may result in data corruption, communication loss, or instability in the control system.
6. Is the TB851 compatible with all AC 800M controllers?
Yes, it is compatible with all controller models that use the CEX-Bus, including PM861, PM864, PM865.
7. What are its environmental tolerances?
It operates between 0°C and 55°C, with humidity up to 95% non-condensing.
8. Can it be reused in other projects?
Yes, it is reusable and does not degrade under normal operational conditions.
9. How do I know it’s working correctly?
As a passive device, it doesn’t generate a status, but communication stability typically confirms proper operation.
10. Is the TB851 RoHS compliant?
Yes, it complies with RoHS and WEEE directives for environmental safety.
Related Models from the Same Series or Function Group
| Model Number | Description | Function | Compatibility | Dimensions (mm) | Weight (kg) |
|---|---|---|---|---|---|
| TB810 | Power Terminal Unit | Power distribution for I/O | S800 I/O | 60 × 25 × 60 | 0.08 |
| TB820 | Terminal Base Unit | Base for I/O modules | S800 I/O | 110 × 35 × 80 | 0.12 |
| TB840 | Module Bus Terminator | Bus termination | S800 I/O | 60 × 20 × 60 | 0.05 |
| TU810V1 | Terminal Unit (8 channels) | I/O Wiring Interface | S800 I/O | 120 × 50 × 70 | 0.18 |
| TU830V1 | Terminal Unit (16 channels) | Extended I/O wiring | S800 I/O | 120 × 50 × 70 | 0.25 |
| TB820V2 | Terminal Base (enhanced version) | Base for I/O | S800 I/O | 110 × 35 × 80 | 0.13 |
Popular ABB Modules Across Automation Platforms
| Model Number | Description | Function | System | Weight (kg) |
|---|---|---|---|---|
| PM864A | AC 800M CPU Module | Controller Unit | ABB 800xA | 1.5 |
| AI810 | Analog Input Module (8 channels) | Analog Signal Acquisition | S800 I/O | 0.65 |
| DO810 | Digital Output Module (16 channels) | Discrete Signal Output | S800 I/O | 0.6 |
| CI854AK01 | Profibus-DP Communication Module | Fieldbus Interface | AC 800M | 0.35 |
| PM865 | Redundant Controller Unit | High Availability Control | 800xA | 1.6 |
| CP6601 | HMI Operator Panel | User Interface & Display | Control Builder | 1.8 |
