Yokogawa ALR121-S00 Serial Communication Module | RS-422/RS-485

Yokogawa ALR121-S00 Serial Communication Module - Dual-Port RS-422/RS-485 Interface

The Yokogawa ALR121-S00 (Part Number: 81AOG000802) is a professional-grade dual-port serial communication module designed for seamless integration with Yokogawa CENTUM DCS and STARDOM control platforms. This module provides robust RS-422/RS-485 serial connectivity, enabling reliable data exchange between distributed control systems and field instrumentation across industrial automation environments.

Technical Specifications

• Model Number: ALR121-S00
• Part Number: 81AOG000802
• Communication Ports: 2 independent serial ports
• Protocol Support: RS-422 and RS-485 (software selectable)
• Baud Rate Range: 300 bps to 115.2 kbps
• Data Format: 7 or 8 data bits, 1 or 2 stop bits, parity options (none/even/odd)
• Electrical Isolation: 1500V DC channel-to-system isolation
• Operating Temperature: -20°C to +60°C (-4°F to +140°F)
• Power Consumption: 3.5W maximum (typical 2.8W)
• Mounting: Standard Yokogawa I/O module rack
• Compliance: CE, UL, FM, CSA certified

Advanced Features & Capabilities

Dual-Port Architecture: Two independent serial communication channels allow simultaneous connection to multiple field devices or integration with legacy equipment, reducing infrastructure complexity and cabling costs in retrofit projects.

Protocol Flexibility: Software-configurable RS-422/RS-485 modes provide versatility for point-to-point (RS-422) or multi-drop network topologies (RS-485), supporting up to 32 devices per port in RS-485 mode.

Galvanic Isolation: Built-in 1500V isolation protects control systems from electrical noise, ground loops, and voltage transients common in industrial environments with heavy machinery and variable frequency drives.

Hot-Swappable Design: Field-replaceable module supports online maintenance without system shutdown, minimizing production interruptions and enabling proactive maintenance strategies.

Industrial Application Scenarios

The ALR121-S00 excels in diverse process automation and manufacturing applications:

Flow Meter Integration: Connects Modbus RTU flow meters, totalizers, and custody transfer systems in oil & gas pipelines, water distribution networks, and chemical batch processing facilities.

Analyzer Communication: Interfaces with gas chromatographs, pH analyzers, dissolved oxygen sensors, and spectrophotometers in pharmaceutical manufacturing, wastewater treatment, and environmental monitoring stations.

Variable Speed Drive Control: Establishes serial links to VFDs controlling pumps, compressors, and conveyor systems, enabling centralized speed control and diagnostic monitoring from DCS operator stations.

Legacy System Migration: Bridges modern DCS platforms with existing serial-based PLCs, RTUs, and proprietary controllers during phased automation upgrades, protecting capital investments while improving operational visibility.

System Integration & Configuration

The ALR121-S00 integrates seamlessly with Yokogawa CENTUM VP, CENTUM CS 3000, and ProSafe-RS systems through standard I/O backplane connections. Configuration is performed via Resource Configurator software, supporting protocol templates for Modbus RTU, ASCII, and custom serial protocols. The module's dual-port capability enables simultaneous polling of multiple device networks or redundant communication paths for mission-critical applications.

Advanced diagnostics include communication error counters, buffer overflow detection, and port status indicators accessible through DCS faceplates, accelerating troubleshooting and reducing mean time to repair (MTTR) by up to 40% compared to non-diagnostic serial interfaces.

Solution Benefits

• Reduces wiring complexity through dual-port design supporting multiple device networks
• Ensures data integrity with electrical isolation and error detection mechanisms
• Lowers total cost of ownership through hot-swappable maintenance and long service life
• Accelerates commissioning with pre-configured protocol templates and intuitive setup tools
• Enhances system reliability with proven Yokogawa quality and global support infrastructure

Related Products

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Quality Assurance

Manufactured under ISO 9001:2015 quality management systems with full traceability. Each module undergoes rigorous factory acceptance testing including burn-in cycles, communication protocol verification, and environmental stress screening to ensure field-ready reliability.

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