Communications Card Description ZB4-606-IF1, DeviceNet 6-7
Moeller 07/01 AWB-C2700-1347GB
5.3 Shielding / Potential equalization
Shielded cables must be used for bus interconnection. The cable braid must be connected at each node with
the lowest possible impedance to the shield reference potential. The connection between the cable shield and
the shield reference potential (on the MV4 to the metallic casing), must be implemented via the connector
casing and the fixing screws of the Sub-D connector.
The shield reference potential of the individual nodes is usually connected to the protective circuit. For this
reason, it is possible that potential equalization currents will result on the cable shield due to the potential
differences. Provide a potential equalization conductor where large potential differences resulting in high
potential equalization currents between the shield reference potentials are the case.
If the hardware to be connected and the PLC (or another communication node) are installed in different
control panels, and the cable shield is directly or indirectly connected to the protective ground on the PLC
side, a potential equalization conductor with a suitable cross-section must be installed between the control
panels. This will prevent the occurrence of large equalizing currents on the shield and shield connections,
similar to those which can occur on the protective circuit during short-circuits.
5.4 Communication cable considerations (EMC)
The design of the Bus cable on the DeviceNet is a significant factor for influencing reliable operation as well
as for the electromagnetic compatibility (EMC) of the communication card and the hardware to which it is
connected.
WARNING! The EMC related values (immunity and emission) stated in the technical data of the
hardware which is to be connected, can only be guaranteed if the following
prescribed cable design features are observed.
The communication cables must be shielded. The cable shield must be made from copper braid. Only use a
metal or metallised connector casing. Install the cable in the connector so that the cable strain relief clamp
pushes the shield directly against the conductive connector casing. This will ensure that the cable shield is
correctly connected to the enclosure of the hardware to be connected via the metallic protective casing of the
connector.
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