Product Overview

The Yokogawa ALR121-S00 S1 is a specialized serial communication interface designed for the CENTUM VP Distributed Control System (DCS) and ProSafe-RS safety systems. This module provides a robust gateway for integrating external subsystems—such as Programmable Logic Controllers (PLCs), motor protection relays, and power analyzers—directly into the control station environment. By utilizing RS-422 and RS-485 physical layers, the ALR121-S00 S1 facilitates high-integrity data exchange over distances reaching 1200 meters. Its architecture is specifically engineered to ensure that communication tasks remain isolated from core safety logic, preventing external data traffic from compromising system-critical safety loops.

Technical Characteristics

The ALR121-S00 S1 is built to industrial standards for high-availability networking and subsystem integration:

Flexible Protocol and Master/Slave Support The module features built-in Modbus RTU slave functionality, allowing a central DCS master or external HMI systems to read from and write to the control station securely. Additionally, it supports subsystem communication, enabling the DCS to act as a master when gathering diagnostic data from diverse third-party hardware.

Advanced Signal Range and Topology Supporting both point-to-point (RS-422) and multi-point (RS-485) configurations, the module manages reliable transmission across expansive plant sites. It effectively maintains signal purity even at the maximum cable length of 1.2 kilometers, provided appropriate shielded twisted-pair cabling is utilized.

Configurable Communication Parameters To ensure compatibility with a wide range of legacy and modern equipment, the ALR121-S00 S1 offers adjustable transmission speeds from 1200 bps to 38400 bps. Users can configure data bits, stop bits, and parity (none, even, or odd) to align with specific device requirements.

Efficient Hardware Design With a current consumption of just 0.5A at 5V DC, the module is optimized for low thermal dissipation within high-density I/O racks. Field wiring is secured through durable terminal block screws, providing a vibration-resistant connection suitable for heavy industrial environments.

Technical Specifications

• Brand: Yokogawa

• Model Number: ALR121-S00 S1

• Product Type: Serial Communication Module

• Interface Standards: RS-422, RS-485

• Protocol Support: Modbus Slave, Subsystem Communication

• Transmission Distance: Up to 1200 meters

• Baud Rate: 1200 to 38400 bps

• Power Consumption: 0.5 A

• Isolation: Independent of safety control loops

• Weight: 0.3 kg

• Dimensions: 3.3 x 10.7 x 13 cm

• Origin: Japan

Application Areas

The Yokogawa ALR121-S00 S1 is frequently deployed in the following scenarios:

• Safety Instrumented Systems (SIS): Exporting non-safety data from ProSafe-RS to a standard DCS for visualization.

• Power Management: Interfacing with Intelligent Electronic Devices (IEDs) for electrical monitoring.

• Warehouse Automation: Connecting to local PLC-controlled conveyor systems or packaging lines.

• Petrochemical Refining: Long-distance data retrieval from remote telemetry units (RTUs) at tank farms.