Product Overview

The Yokogawa ALR121-S50 S1 is a high-performance Serial Communication Module designed for the CENTUM VP and CENTUM CS 3000 Distributed Control Systems (DCS). This module functions as a sophisticated gateway, enabling the Field Control Station (FCS) to interface with various third-party subsystems—including PLCs, power monitors, and analytical instruments—via RS-422 or RS-485 protocols.

Engineered for mission-critical reliability, the ALR121-S50 S1 supports dual-redundancy. When paired in adjacent slots, these modules create a fault-tolerant communication link where data is synchronized in real-time. This ensures that in the event of a port or module failure, the control logic seamlessly transitions to the standby unit without data loss or process interruption, maintaining high system availability in demanding industrial environments.

Technical Specifications

• Manufacturer: Yokogawa

• Model Number: ALR121-S50 S1

• Interface Type: Serial (RS-422 / RS-485)

• Number of Ports: 2 ports per module

• Transmission Speed: 300 bps to 115.2 kbps

• Communication Distance: Maximum 1200 meters (total cable length)

• Redundancy: Supports Dual-Redundant configuration

• Isolation: 500 V AC between signal and system

• Weight: 0.30 kg

• Dimensions: 32.8 mm x 141 mm x 130 mm

• Current Consumption: Max. 0.5 A (5 V DC)

• Origin: Japan

Advanced Operational Features

• Intelligent Data Equalization: The module implements a proactive data-sync mechanism where the standby unit continuously updates its output image data, ensuring it is ready to assume control instantly upon failover.

• Subsystem Integration: Acts as a Modbus Master or Slave (with appropriate software) to collect data from disparate field devices and integrate them into the global DCS database.

• Hot-Swappable Design: To minimize downtime, the ALR121 can be replaced online while the redundant partner maintains active communication.

• Status Diagnostics: Equipped with onboard LED indicators to provide real-time status of data transmission (TX), reception (RX), and module health (Ready/Fail).

• Versatile Application: Widely utilized in oil and gas, power generation, and chemical processing industries for integrating specialized hardware into the primary control network.