Yokogawa SNT401-53/CU1N Optical ESB Bus Repeater Overview

The Yokogawa SNT401-53/CU1N is an optical ESB bus repeater master module for Yokogawa DCS systems. The "5" suffix indicates operation with no explosion protection. The "3" suffix specifies ISA Standard G3 compliance with an extended temperature range of -20 to 70°C. The CU1N suffix identifies the connector unit specifically designed for ESB bus applications. This module provides ESB bus optical transport function for extending communication distances. Consequently, the SNT401-53/CU1N enables remote I/O placement far from the main controller.

Connection & Topology Options

The Yokogawa SNT401-53/CU1N supports multiple connection methods for installation flexibility. Star type connection allows one master to communicate with multiple remote nodes. Chain type connection enables daisy-chaining of repeaters for extended reach. Furthermore, the module is available for both star and chain type connections simultaneously. Number of connecting stages reaches a maximum of two stages for complex network architectures. Therefore, the SNT401-53/CU1N adapts to various plant layouts.

Transmission Distance

The Yokogawa SNT401-53/CU1N delivers impressive transmission distance capabilities. Maximum transmission distance is 5 km total across two stages under standard conditions. However, in a Vnet/IP system with R1.03 or later firmware, the total distance increases. Specifically, two stages can achieve a maximum of 10 km total distance. As a result, the SNT401-53/CU1N supports very large distributed control system architectures. This long-distance capability allows central control rooms to connect to remote I/O cabinets across large facilities.

Environmental & Power Specifications

The Yokogawa SNT401-53/CU1N withstands harsh industrial environments. The "3" suffix provides ISA Standard G3 compliance for corrosive atmosphere resistance. Extended operating temperature range spans -20 to 70°C for extreme installation locations. Current consumption is 0.5 A from the system backplane. Total weight is approximately 0.3 kg for easy handling and mounting.

Key Features & Benefits

• Dual topology support – The SNT401-53/CU1N works with star or chain type connections.

• Long transmission distance – Reaches up to 5 km standard or 10 km with Vnet/IP R1.03.

• Two-stage cascading – Connect up to two repeater stages for extended network reach.

• ISA G3 compliant – Withstands corrosive atmospheres in chemical and refinery environments.

• Wide temperature range – Operates reliably from -20°C to 70°C.

• ESB bus optical transport – Enables fiber optic communication for noise immunity.

Installation Guidelines

Follow these steps to install the Yokogawa SNT401-53/CU1N correctly. First, power down the Yokogawa CENTUM system completely. Second, select an available slot in the ESB bus repeater rack. Third, align the SNT401-53/CU1N with the card guides in the chassis. Fourth, push the module firmly into the backplane connector until seated. Fifth, secure the module with the retaining screws at top and bottom. Finally, connect the optical fiber cables to the CU1N connector unit.

For star topology, connect each remote node directly to the SNT401-53/CU1N. For chain topology, cascade the first repeater output to the second repeater input. Ensure total distance does not exceed 5 km (or 10 km for Vnet/IP R1.03+ systems). Use only Yokogawa approved optical fiber cables for reliable communication.

Package Contents

Your shipment includes the following items:

• 1 x Yokogawa SNT401-53/CU1N optical ESB bus repeater master module

• 1 x Installation manual with topology diagrams

• 1 x CU1N connector unit (pre-attached)

• 1 x Dust cap set for unused optical ports

No optical fiber cables are included with the SNT401-53/CU1N. Therefore, you must order these separately based on your distance requirements. Likewise, no additional repeater modules are provided for two-stage configurations.

Frequently Asked Questions (FAQ)

1. What is the difference between star and chain connection?
Star connection on the SNT401-53/CU1N connects one master to multiple remote nodes directly. Chain connection cascades repeaters in series for extended distance.

2. What is the maximum number of connecting stages?
The Yokogawa SNT401-53/CU1N supports a maximum of two connecting stages. Therefore, you can cascade up to two repeaters in a chain configuration.

3. Can I achieve 10 km distance with any system?
No. The 10 km total distance on the SNT401-53/CU1N requires Vnet/IP system with R1.03 or later. Standard systems are limited to 5 km.

4. What does the ISA G3 rating mean?
ISA G3 rating on the SNT401-53/CU1N indicates corrosion resistance for harsh environments. This suits chemical plants, refineries, and offshore platforms.

5. Is this module compatible with CENTUM VP?
Yes. The Yokogawa SNT401-53/CU1N integrates with CENTUM VP and other Yokogawa DCS systems using ESB bus communication.