There are more profibus DP Fieldbus nodes installed than any other network (by a big margin). And that doesn't mean there won't be a problem with the network. The experts point to these five common issues:
1. Terminator. The number one most common issue– the cable ends at a PROFIBUS device connected with a DB9 connector. The connector has a switch to enable the terminator. A terminator is required at the end of the line. Someone forgot to throw the switch.
2. Wrong cable. Don't use telephone cable as we saw in one installation. Use actual PROFIBUS cable; it's available from dozens of suppliers.
3. Wrong distance for baud-rate. PROFIBUS DP can be run at different baud-rates. The higher the baud-rate, the shorter the allowed cable distance. Check your installation against the PROFIBUS Installation Guidelines.
4. Shield continuity through a connector. The shield has to properly exposed and installed in the connector. Do a visual check.
5. PROFIBUS cable installed next to the power cable. PROFIBUS, like any digital network, is susceptible to electromagnetic interference. Don't tie wrap the PROFIBUS cable to the power cable! Maintain the separation specified in the PROFIBUS Installation Guidelines. And, of course, if you are in an area where interference is unavoidable, use fiber optic cable instead of copper.
Maintaining a network with “Tips” alone is not sufficient; you need deeper knowledge. At a minimum, download the multiple PROFIBUS Installation Guidelines. Better yet, attend a complete PROFIBUS Certified Network Engineer class. Or contact the PROFI Interface Center for a hands-on, onsite Installers' class.
