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ABB TB851 (Order Code: 3BSC950194R1) CEX Bus Terminator 

1. Key Parameters

• Product Model: TB851
• Order Code/Part Number: 3BSC950194R1 (unique identifier for procurement and legacy system compatibility verification)
• Core Function: Terminates CEX bus segments in ABB Advant OCS; eliminates signal reflections, filters EMI, and stabilizes data communication between controllers and I/O modules
• Bus Compatibility:
  • Target Bus Type: ABB proprietary CEX (Control Expansion) bus (used for inter-module communication in Advant OCS)
  • Supported Systems: Advant OCS MasterPiece controllers, Advant OCS I/O modules (e.g., AI810, DI810), and CEX bus racks
• Electrical Specifications:
  • Termination Resistance: 120Ω (fixed, matched to CEX bus characteristic impedance)
  • Signal Voltage Level: 0~5V DC (compatible with CEX bus logic levels)
  • Insulation Voltage: 1kVrms (between bus circuit and ground; prevents ground loops)
  • EMI Filtering: Integrated low-pass filter (cutoff frequency: 500kHz; reduces high-frequency noise)
  • Input/Output (I/O) Connections: 4-terminal screw block (for CEX bus positive, negative, and shield)
• Mechanical Specifications:
  • Dimensions (W×H×D): 32mm × 175mm × 220mm (1-module width, fits Advant OCS standard CEX bus racks)
  • Mounting: Rack-mounted (dedicated slot in Advant OCS 400-series enclosures; tool-less installation via snap-in clips)
  • Terminal Type: Screw terminals (accepts 0.5mm²~1.5mm² copper conductors; torque range: 0.5~0.8N·m)
  • Weight: Approximately 270g
  • LED Indicators: 1× green LED (bus power present); 1× yellow LED (bus activity detected)
• Environmental Ratings:
  • Operating Temperature Range: 0℃~+60℃ (32℉~140℉)
  • Storage Temperature Range: -20℃~+70℃ (-4℉~158℉)
  • Humidity Tolerance: ≤90% RH (non-condensing, 40℃)
  • Vibration Resistance: 5~500Hz, 1g acceleration (IEC 60068-2-6; no mechanical failure)
  • Shock Resistance: 20g acceleration (11ms duration, IEC 60068-2-27; maintains impedance matching)
• Compliance Standards: IEC 61000-6-2 (EMC immunity for industrial environments), EN 60947-1 (low-voltage control equipment), UL 508 (industrial safety)

2. Key Features

• CEX Bus Impedance Matching: Fixed 120Ω termination resistance aligns with the CEX bus’s characteristic impedance, eliminating signal reflections that cause data corruption (e.g., bit errors, frame loss) in long bus segments (≥50m)—critical for large Advant OCS installations (e.g., refineries, chemical plants).
• Integrated EMI Suppression: Low-pass filter blocks high-frequency noise from industrial equipment (e.g., motors, transformers, inverters), ensuring stable communication even in noisy process environments where legacy systems lack advanced noise mitigation.
• Legacy Advant OCS Compatibility: Designed as a drop-in replacement for older ABB CEX terminators (e.g., TB850), with identical mounting and electrical interfaces—no modifications to existing Advant OCS racks or wiring required, simplifying retrofits.
• Clear Status Monitoring: Dual LEDs (power + activity) provide real-time feedback on bus health: green LED confirms power to the terminator, while yellow LED indicates active data transmission—enabling quick troubleshooting of bus faults (e.g., dead segments, no communication).
• Robust Insulation: 1kVrms insulation between the CEX bus circuit and ground prevents ground loops—a common issue in distributed legacy systems with multiple grounding points—avoiding communication disruptions or module damage.
• Industrial-Grade Durability: Withstands the temperature range (0℃~+60℃) and vibration typical of legacy industrial sites, ensuring reliable performance in aging facilities where environmental control may be limited.
• Compact Rack-Mount Design: 32mm width fits standard Advant OCS racks, preserving space for other critical modules (e.g., controllers, I/O cards) and maintaining the system’s modular architecture.

3. Application Fields

• Advant OCS Legacy System Maintenance: Terminates CEX bus segments in chemical, petrochemical, and power plants operating ABB Advant OCS—supporting continued operation of legacy control systems until full modernization.
• Process Industry Retrofits: Used in retrofits of older Advant OCS installations (e.g., replacing failed terminators) to restore CEX bus integrity, ensuring uninterrupted communication between MasterPiece controllers and I/O modules.
• Power Generation Auxiliaries: Stabilizes CEX bus communication in legacy thermal power plants, where Advant OCS controls auxiliary equipment (e.g., boiler feed pumps, cooling fans)—preventing downtime in critical power infrastructure.
• Oil & Gas Midstream Operations: Deployed in older pipeline monitoring and pumping stations with Advant OCS, maintaining CEX bus reliability for sensor data transmission (e.g., pressure, flow) and valve control.
• Water & Wastewater Treatment (Legacy Plants): Supports CEX bus segments in municipal wastewater treatment plants using Advant OCS, ensuring consistent communication between process controllers and aeration/mixing equipment.
• Food & Beverage Batch Processing: Terminates CEX buses in legacy batch lines (e.g., dairy, brewing) controlled by Advant OCS, preserving recipe execution and temperature control until system upgrades.

4. Precautions

• System Compatibility: Use exclusively with ABB Advant OCS CEX bus networks. Installation in non-CEX systems (e.g., Profibus, Modbus) will mismatch impedance, causing signal degradation or bus failure.
• Termination Placement: Install only at the physical end of CEX bus segments. Mid-segment termination disrupts signal flow, while missing end termination creates reflections—both lead to communication errors or complete bus failure.
• Impedance Integrity: Do not modify or replace the fixed 120Ω resistor. Damage to this component breaks impedance matching, rendering the terminator ineffective and risking data loss in the CEX bus.
• Grounding Requirements: Connect the terminator’s ground terminal to the Advant OCS rack’s common ground (resistance ≤1Ω). Poor grounding reduces EMI filtering effectiveness and increases susceptibility to noise.
• Wiring Best Practices:
  • Use shielded twisted-pair (STP) cables for CEX bus connections (0.5mm²~1.5mm² copper conductors).
  • Ground the cable shield at both ends (bus start and terminator end) to enhance EMI protection.
  • Route CEX bus cables away from high-voltage power lines (≥30cm spacing) to minimize interference.
• Environmental Protection: Install in a sealed Advant OCS rack enclosure in harsh environments (e.g., dusty, corrosive). Avoid exposure to temperatures beyond 0℃~+60℃ or direct moisture, which accelerates component degradation.
• Legacy Spare Management: As a legacy component, spare availability may be limited. Maintain a stock of TB851 units for critical Advant OCS systems, or consult ABB for migration strategies to modern bus systems (e.g., Profinet) if long-term support is needed

The structure and details of the product：

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