ALR121-S51 Yokogawa Serial Communication Module

Hardware Specifications

DCS Serial Communication and Field Network Interface

The Yokogawa ALR121-S51 performs serial communication between Yokogawa control stations and external intelligent devices. It exchanges process data, status information, and diagnostic signals through RS-422 or RS-485 electrical interfaces.

The module supports both point-to-point and multipoint network structures. Therefore, it can connect PLC systems, motor control centers, power monitoring equipment, analyzers, and other serial communication devices.

For Yokogawa CENTUM platforms, the module supports configured communication parameters including transmission speed, character length, stop bits, and synchronization method. The RS-485 multipoint mode allows multiple field devices to share the same communication network.

Frequently Asked Questions

Q: What serial interfaces does the Yokogawa ALR121-S51 support?
A: The ALR121-S51 supports RS-422 and RS-485 interfaces using a 4-wire system configuration. It supports both point-to-point and multipoint communication methods.

Q: What communication mode does the ALR121-S51 use?
A: The module uses half-duplex communication with start-stop synchronization and binary transmission coding.

Q: Can the ALR121-S51 connect third-party serial devices?
A: Yes. The module can communicate with external serial devices such as PLCs, analyzers, and monitoring equipment when communication parameters match the configured settings.

Field Installation Guidelines

Install the ALR121-S51 according to the Yokogawa hardware installation manual and the target CENTUM system configuration requirements.

Use shielded communication cables for RS-422 and RS-485 wiring. Connect cable shields according to the site grounding practice to reduce electrical interference.

Separate serial communication cables from high-voltage power lines and high-current motor cables. Maintain correct terminal polarity for RS-422 and RS-485 signal pairs during installation.

Verify communication settings including baud rate, character length, stop bits, and synchronization mode before connecting external equipment.

Confirm module status indicators and communication diagnostics after installation to ensure correct data exchange between the control system and connected devices.