Greetings everyone, I recently visited a customer who is experiencing communication errors on their RS-485 Modbus network. The PLC communicates with around twelve drives, and despite adjusting the communication error time to 90 seconds, the issue persists. During my latest visit, I observed a wave-form that showed clean edges, making termination issues seem unlikely. However, the cables are disorganized and surrounded by numerous power cables. Despite proper termination and shielding, the source of the problem remains unclear. I will be returning soon for further investigation and would appreciate any insights on the probable source of the issue. Apologies for the upside-down picture. Thank you for any assistance. Yosi
Should the shield be terminated in the connector or secured with a large grounding clamp on the bus bar?
Has the system been functioning properly previously? Have any new devices been added recently? How is the wiring connecting each unit on the bus? You may want to try removing devices from the bus to pinpoint any specific connection issues. This troubleshooting method can help in isolating the source of the problem.
Reduce high frequency noise levels of over 2 volts emanating from VFD outputs by utilizing VFD rated cables for motor output leads or implementing shielding. To further minimize interference, separate RS485 lines from motor wires and incorporate snap-on ferrite cores to RS485 cables. This will help in optimizing the performance and reliability of your system.
In a discussion forum, JesperMP questioned whether a shield should be terminated in the connector or with a robust clamp on the ground bus bar. Ultimately, the consensus seemed to lean towards using a big, sturdy clamp on the ground bus bar for optimal grounding.
Skorp inquired about the functionality of the equipment and any recent installations on the bus. The wiring of each unit was questioned, suggesting disconnecting devices to pinpoint any issues along a specific path. Although the devices eventually respond, there are concerns about the overall performance. Troubleshooting steps will involve disconnecting and reconnecting devices one at a time. Additionally, a suggestion was made to remove the uLogix from the panel for assessment. Any potential new equipment has not been disclosed, but further investigation into the cabling is a priority. Appreciation was expressed for the provided input.
✅ Work Order Management
✅ Asset Tracking
✅ Preventive Maintenance
✅ Inspection Report
We have received your information. We will share Schedule Demo details on your Mail Id.
Answer: - Common causes of communication errors on an RS-485 Modbus network can include improper termination, noise interference from surrounding power cables, cable disorganization, and inadequate shielding.
Answer: - Adjusting the communication error time can help in allowing more time for the network to recover from errors before triggering additional responses, but it may not necessarily resolve the underlying cause of the communication errors.
Answer: - Steps to troubleshoot RS-485 communication errors can include checking for proper termination, ensuring adequate shielding, organizing cables to minimize interference, and investigating potential sources of noise such as nearby power cables.
Answer: - Proper cable organization and shielding are crucial in preventing communication errors on an RS-485 Modbus network as they help reduce noise interference and maintain signal integrity.
Answer: - When facing persistent communication errors despite proper termination and shielding, factors such as ground loops, signal reflections, device configuration mismatches, and potential sources of electromagnetic interference should be thoroughly
Join hundreds of satisfied customers who have transformed their maintenance processes.
Sign up today and start optimizing your workflow.