Description
The Yokogawa ALR121-S00 is a dual-port serial communication module designed for Field Control Station (FCS) integration within Yokogawa CENTUM CS, CENTUM CS 3000, and CENTUM VP distributed control system (DCS) architectures. It manages half-duplex serial data exchanges using RS-422 or RS-485 physical layers, enabling seamless connectivity with third-party subsystems, programmable logic controllers (PLCs), multivariable transmitters, and analyzer packages.
Technical Specifications
| Parameter | Value |
| Manufacturer | Yokogawa Electric Corporation |
| Product Type | Serial Communication Module (FIO / Field Control Unit) |
| Model Code / Suffix | ALR121-S00 (Standard Type, Basic Version, Non-explosion protection) |
| Communication Interface | RS-422 / RS-485 (4-wire system, 2 independent ports) |
| Connection Method | Point-to-point (RS-422); Multipoint / multidrop (RS-485) |
| Transmission Speed | 1200, 2400, 4800, 9600, 19200, 38400 bps (subsystem dependent) |
| Synchronization | Start-stop synchronization |
| Transmission Distance | Maximum 1,200 m total extended length |
| Current Consumption | 0.5 A (24 V DC nominal bus power supply) |
| Operating Temperature | −10°C to +60°C |
| Physical Dimensions | 32.8 mm (W) x 126.7 mm (H) x 130 mm (D) |
| Weight | Approx. 0.34 kg |
Availability and Commercial Terms
- Condition Options: New Original (Factory Sealed), New Surplus, or Refurbished (fully bench-tested)
- Lead Time: 1 to 3 business days for stock items; 2 to 4 weeks for specialized or factory-sourced units
- Warranty: 12-month standard replacement warranty from date of shipment
- Pricing Note: Listed price is indicative, not final. Price subject to market conditions; contact us for a firm quote.
Engineering and Integration Notes
The ALR121-S00 installs directly onto standard Yokogawa Field Control Units (such as AFV30, AFV40, AFV10) or ESB/ER node units to handle external serial communication drivers like Modbus RTU, Yokogawa FA-M3 link protocols, or proprietary vendor packages.
- Wiring & Termination: The module utilizes dual front-facing terminal blocks with M4 screws for secure signal termination. For RS-485 multi-drop configurations, ensure proper biasing and 120-ohm termination resistors are installed at both physical ends of the trunk line to eliminate signal reflections.
- Shield Grounding: Terminate multi-pair shielded cables (such as AKB161 or AKB162) to the cabinet ground bar strictly at one end to prevent ground loops and common-mode noise corruption across long 1,200 m serial runs.
- Software Configuration: Define port parameters (baud rate, data bits, stop bits, and parity) precisely within the Yokogawa System Builder software to match the attached field device specifications prior to downloading station definitions.
Frequently Asked Questions
What is the difference between the ALR111 and the ALR121-S00?
The ALR111 utilizes an RS-232C interface configured for short-distance point-to-point connections (maximum 15 meters). Conversely, the ALR121-S00 features RS-422/RS-485 interfaces capable of long-distance communication (up to 1,200 meters) and multi-drop network topologies.
Can the ALR121-S00 module be hot-swapped during operation?
Yes, when implemented within supported FIO node configurations and redundant controller frameworks, the module can be replaced without cutting power to the entire node rack. However, removing the module will temporarily sever communication on its two active serial channels, so verify process state and loop safety before extraction.
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