Each electrical cable can, in principle, cause or suffer electronic magnetic interferences due to the coupling effect. To ensure electromagnetic compatibility (EMC), a cable must be electrically shielded. This protective effect is expressed above all by the indication of the so-called optical coverage of the shield. This is the area that is optically covered by the shield. For example, if the cable has a copper foil as its shield, it can be said to have 100% coverage because it acts like a tube. If the shield is braided or surrounded with wires, this has the advantage that, in contrast to the foil, the shield is not affected by movement. However, there is the disadvantage that the coverage area decreases because there is a small gap between each shield wire.
For cables in linear motion, it has been found that a braided shield with high coverage and optimal braid angle is the best solution. On the other hand, if it is a torsion cable, the optimum is a covered shield bedded on sliding material. The best result with the shielding offers an optical coverage of 90%.