Galvanic Isolator Helps Overcome Issues When Adding New Devices to a Legacy Modbus RTU System

Background

A customer in the oil and gas industry needed to monitor additional pressures across existing systems in the field. To support the upgrade, they added two Banner S15C-PS150SS-MQ pressure sensor/converter assemblies to a legacy Modbus RTU RS-485 communications platform that had been in operation for more than 10 years and included third-party Modbus control and field devices.

Challenge

Communication issues emerged within the legacy Modbus RTU RS-485 network during the system upgrade. This is a common challenge when adding new devices to older serial networks, especially when legacy third-party equipment is already in place. Testing showed that existing network conditions and connected third-party Modbus devices were affecting communication with the newly added Banner S15C converters.

Solution

To resolve the issue, a Banner S25GI-RS485-Q Galvanic Isolator was installed ahead of the S15C converters to isolate both power and Modbus RTU communications from the rest of the network. The installation also included an S15YB-M124-M124-0.2M splitter cable positioned just before the converters connected to the Modbus RTU trunk line.

The galvanic isolator enabled the customer to complete the upgrade and gain access to critical pressure data from the new Banner sensors through the existing legacy Modbus system, without costly infrastructure changes.