Brochure/Catalogue

The following pictures show examples of use:
Shield connection via functional earth
Shield connection on common earth
Shielding
In practice, the shield is often twisted and connected to
a terminal point. There is very high attenuation (voltage
drop) on these connections, especially for high-frequency
interference. Therefore this type of shielding should not
be used, even for short cable lengths. The cable shield is
practically negated and can, at best, be helpful for low-
frequency interference. We recommend a large, extensive
contact with the braided shield of the cable.
There are four main types of coupling:
• Galvanic coupling
• Capacitive coupling
• Inductive coupling
• Radiation coupling
Such interferences usually occur mixed together, but they
can be categorised as follows:
• Electromagnetic elds
• Ripple voltage (50 Hz)
• Lightning
• Interference pulses (current, voltage)
• Transient surge voltages
• Radio interference
• ESD (electrostatic)
• Burst
• Mains feedback
The conductor “ow” is another detail for concern with the
shield contact. The temperature changes caused by the
current ow lead to changes in the wire’s diameter. A rigid
contact can therefore only be partially effective. A self-
adjusting contact is what is really required. Weidmüller’s
clamping yoke products (KLBÜ) provide the perfect solution
for this challenge.
Earthing for shielded cables
B
B.122 2028840000
Lightning and surge protection for control and instrumentation signals