Yaskawa Profibus-DP Option Card CM061 - Manual (Page 62)

Troubleshooting D-10
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Common Mode Voltage Between Any Two Points Is Less Than 7vdc.
RS485 requires that the common mode voltage be less than 7vdc. Large voltage potential differences between points on the network, may
cause equalization current flow in the shield. This interferes with the PROFIBUS-DP signal quality. If common mode voltage is greater
than 7vdc, a separate ground conductor must connect the network devices to a central ground point, typically at the start of the segment.
# Shield Is Continuous And Both Ends Of The Shield Are Grounded.
The cable shields, between all nodes of the network segment shall be connected, to form a single conduction path throughout the segment.
The shield must then be grounded at each endpoint
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Cable Is Routed Correctly
The PROFIBUS-DP network cable must not run parallel to or close to any high power or high frequency cables. A minimum clearance of
4” – 10” is required, depending on the level of voltage or signals in the cables. If network cables must cross high power or frequency
cables, they must do so at a 90 deg angle.