Cable Shields

• Only use shielded data cables. The shield should be earthed at both ends. Make sure that no parasitic currents can flow through the cable shields. This can be done by installing current-carrying equipotential bondings.
• A cable shield only earthed at one end can only protect from capacitively coupled interference and low-frequency disturbances (50 Hz hum).
• Use only cables with braided shields. Foil shields are not robust enough, cannot be contacted well and have poor HF properties.
• Only use metallic or metal-plated plugs for shielded data cables.
• For analog signals, only use shielded cables. Earth the shield only at one end for small signals.
• Earth the cable shield directly with a clip when entering the switch-gear cabinet. Do not cut the shield until the cable reaches the module connected.
• The connection between the PE bar and the shield bar must have a low impedance.