Inline Isolator Safeguards Modbus RTU Wiring

Banner Engineering has introduced the S25GI galvanic isolator to protect RS485 and Modbus RTU communication networks from electrical noise, ground loops, and surge events. Designed for inline installation with rugged IP67 connectors, the compact device preserves cabinet space while shielding serial signals from interference caused by VFDs and high-voltage equipment. With integrated power pass-through and flexible mounting options, the S25GI simplifies machine retrofits and network expansion.

Banner Engineering S25GI Galvanic Isolator. Image used courtesy of Banner Engineering

Serial Communication

Even in today’s age of modern communication protocols, you will still find RS485 and Modbus RTU used for communications between control systems and devices. The serial protocol is open source and a reliable communication standard; many component manufacturers still use the protocol today. Because RS485 relies on 5VDC TTL logic, it is susceptible to EMI from devices like large VFDs or even power transmission lines. This interference can be reduced by using shielded cables, short cable runs, and routing communication cables away from high-voltage power lines. Banner Engineering has recently released the S25GI, a galvanic isolation device installed in line with your RS485 or Modbus RTU connections, which acts as a filter to remove EMI and power surges that might affect communications.

Grounding Loops and Electrical Faults

A ground loop occurs when multiple devices have different paths to ground, which results in a difference in electrical potential. A ground loop is a common issue in a control cabinet due to the variety of components used in tight spaces, but it is also very easy to avoid. A galvanic isolator is an electrical separator that isolates communication signals and prevents electrical noise interference and possible damage from power surges. These devices are typically installed on a DIN rail within the electrical cabinet and can take up significant space within the control cabinet. The S25GI is installed inline with devices and doesn’t take up any space in the control cabinet.

Magnetic mounting of the S25GI isolator. Image used courtesy of Banner Engineering

Compact Communication Isolation

The S25GI is designed for ModBUS RTU and RS485 communication protocols. The S25GI uses rugged IP67 connections on both sides for a series installation, eliminating the need for field wiring. An integrated 200mA power pass-through allows supply power to flow through the device and power a network of multiple sensors, indicators, or I/O modules. The small device can be installed directly at the sensor for single-point protection or at the communication hub to protect the entire network.

Installation of Modbus converters in a communication panel. Image used courtesy of Wikimedia

Machine Retrofits

Many manufacturers have outdated equipment that needs to be upgraded to support new part types or to run more efficiently. Adding devices to older equipment can be challenging because the system may not be designed to handle the added component. For example, adding a VFD to an older machine using Modbus RTU could cause communication issues. The same is true when adding an RS485 device to a machine that doesn’t use serial communication. By simply installing the Banner S25GI inline with the ModBus communication hub, you can eliminate electrical noise in the ModBus network. Existing noise within the system could cause issues in the new device. Adding a galvanic isolator, such as the S25GI, can simplify integrating the new serial device without additional field wiring or space in the control cabinet.