Hi there Rashid, typically it’s installation-related and can come from ground loops, poor cable installation (running fieldbus cables next to high-voltage cables), or using improper cable types, variable frequency drives, motors or generators in close proximity to fieldbus devices, and a handful of other things. However, one of the benefits of a FOUNDATION Fieldbus type installation is the variety of diagnostic tools available to help troubleshoot and detect these types of fault conditions, as well as assist in troubleshooting poor quality signals and other physical layer fault conditions. Please feel free to contact us at www.pepperl-fuchs.com/usa/en/ask_an_expert_pa.htm if you require further assistance. Thank you.