What does screening mean and what are the advantages and disadvantages of different types of screening?

Foil screens are light and made of comparatively cheap material that increase the cable diameter only insignificantly. They show a low conductivity compared with other cable conductors. Primary a foil screen is applied with low disturbances. As such a screen covers the cable 100 % in case of an appropriate production they are very effective with high frequencies (GHz). In case of mechanical stress however, this construction type is prone to wear.

Metal wire shields are braided around the cable by counter rotation with the help of special machines and multiple wire bundles, the so called folding. The resulting cable section shows the highest conductivity compared to all screening types and therefore, is especially appropriate for high disturbance energy. At the intersections of the wire bundles (folding) gaps occur that limit the effectiveness with high frequencies (>100 MHz). Equally high torsional stress causes restrictions for the braiding of the folding.

Wrapping with metal wires is simply a “half braiding”. The copper wires are wrapped in one direction around the cable. In this way only a smaller section results compared with a metal braiding. As there is no overlapping, there is a higher flexibility for torsional applications. In case of high alternating bending stress however, gaps between the wires may occur more easily than the intersections of a braiding allow.