Description

Yokogawa ALR121-SE1 Serial Communication Module

The Yokogawa ALR121-SE1, also cataloged as the ALR121 Serial Communication Module, operates as a dedicated hardware component for RS-422/RS-485 data exchange within Yokogawa FCS and distributed I/O networks.

Hardware Specifications

Parameter	Specification
ModelBrand	Yokogawa ALR121-SE1
Origin	Japan
Weight	0.30 kg
Dimensions	100 x 160 x 30 mm (3.94 x 6.30 x 1.18 in)
OperatingTemp	-20 to +60 degC
StorageTemp	-40 to +80 degC
HumidityRange	10 to 95% RH, non-condensing
PowerConsumption	0.5 A max @ 5 V DC backplane
Interface	RS-422 / RS-485
Ports	2 independent ports
ConnectionMethod	RS-422: Point-to-point, RS-485: Multi-point
CommunicationMode	Half-duplex, start-stop synchronization
TransmissionCode	ASCII / Binary
BaudRates	1200 / 2400 / 4800 / 9600 / 19200 / 38400 bps
CharacterLength	7 or 8 bits
StopBits	1 or 2 bits
Parity	None, Even, Odd
MaxTransmissionDistance	1200 meters
I/ODataCapacity	1000 words per module
CommunicationDefinitions	Max 128 per module

Process Contro lSystem Features

The ALR121-SE1 incorporates channel-to-channel isolation to prevent cross-interference between RS-422 and RS-485 ports. The module supports standard 4-20 mA HART loop protocols for connected devices and maintains cold junction compensation (CJc) for precise signal integrity under variable thermal conditions. Redundant configurations are supported for critical communication protocols such as Modbus RTU/ASCII and FA-M3, enabling uninterrupted data flow in dual-module setups.

Frequently Asked Questions

Q: Does the ALR121-SE1 support hot-swap replacement within FCS nodes?
A: Yes, the module can be replaced without powering down the node, provided the backplane bus load does not exceed rated limits.

Q: What is the maximum distance for reliable RS-485 communication?
A: RS-485 communication is supported up to 1200 meters with standard twisted-pair cabling.

Q: Are firmware updates required for connecting to different subsystem protocols?
A: No firmware update is needed; protocol selection is configured via the module I/O settings and network parameters.

Field Installation Guidelines

1. Mount the module securely within the FCS node or designated I/O chassis.
2. Ensure RS-422/RS-485 twisted-pair cables are shielded and properly grounded at a single point.
3. Avoid routing signal lines near high-voltage or high-frequency devices to reduce noise pickup.
4. Terminate unused ports according to RS-422/RS-485 standard to maintain signal integrity.
5. Verify dual-port protocol settings before commissioning to avoid communication conflicts.

Specifications

• Brand: Yokogawa

Advantages

• High reliability in industrial environments
• Supports continuous operation
• Compatible with major PLC/DCS systems