D301087 0308 - BL20 CANopen 7-11
Shielding of cables
7
Shielding of cables
Shielding is used to prevent interference from voltages and the radi-
ation of interference fields by cables. Therefore, use only shielded
cables with shielding braids made from good conducting materials
(copper or aluminum) with a minimum degree of coverage of 80 %.
The cable shield should always be connected to both sides of the
respective reference potential (if no exception is made, for example,
such as high-resistant, symmetrical, analog signal cables). Only
then can the cable shield attain the best results possible against
electrical and magnetic fields.
A one-sided shield connection merely achieves an isolation against
electrical fields.
The insulation of the shielded data-cable should be stripped and
connected to the shield rail when the system is not in operation. The
connection and securing of the shield should be made using metal
shield clamps. The shield clamps must enclose the shielding braid
and in so doing create a large surface contact area. The shield rail
must have a low impedance (for example, fixing points of 10 to
20 cm apart) and be connected to a reference potential area.
The cable shield should not be severed, but routed further within the
system (for example, to the switchgear cabinet), right up to the inter-
face connection.
Attention
When installing, please pay attention to the following...
– the shield should be connected immediately when entering the
– system,
– the shield connection to the shield rail should be of low
– impedance,
– the stripped cable-ends are to be kept as short as possible,
– the cable shield is not to be used as a bonding conductor.
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