Understanding the difference between optical coverage and shielding factor
The shielding factor (Kr) is used to determine the optical coverage (F) of the braided shielding of a cable.
Often confused, an optical coverage of 85% corresponds to a shielding factor of 0.617. Requiring a shielding factor of 85% would actually correspond to an optical coverage of nearly 97.8%.
Optical coverage/shielding factor
These are two terms used to characterise the braiding of a cable.
Please note: the main term used in cable specifications is optical coverage.
The optical coverage or shielding factor of braided shielding is the ratio of the shielding surface area to the cable surface area.
The effectiveness of a braided shield will depend on the optical coverage.
How is it defined?
F : Optical coverage
Kr : Shielding factor
Table of equivalence
The higher the optical coverage, the better the protection:
Shielding provides protection against both the transmission and the reception of electromagnetic interference (EMC). It works on the Faraday cage principle, whereby any metal cage with an earth connection prevents magnetic fields from passing through it.
Braided shielding is mainly effective against low-frequency electromagnetic interference. For high-frequency interference, shielding with aluminium tape or mixed shielding (aluminium tape + braid) is recommended.