Peppers Cable Glands Limited
Stanhope Road
Camberley
Surrey
GU15 3BT
United Kingdom
tel.
+44 (0) 1276 64232
fax. +44 (0) 1276 691752
email. admin@peppers.co.uk

EMC and Cable Glands

EMC PROTECTION

All electronics, electrical systems and cable runs emit magnetic and electrical energy, if this energy unintentionally interacts with another device and causes it to malfunction, then it is considered interference. Most EMI is caused by frequencies that fall between 1 KHz and 10 GHz, and this range is known as the RFI band, which includes radio and audio frequencies.

To protect equipment from EMI the earthing/grounding of enclosures and connections has to be engineered so that it has in its simplest form a seamless electrical continuity from point A to point B. The objective is to protect the interior of the system from external environment RFI influences (Susceptibility) and at the same time to protect the external environment from the system (Emission).

Magnetic interference can only be shielded by a ferrous screen of some thickness such as steel enclosures. With electrical energy the susceptibility of a system depends on there being a slot or antenna great than 1/4 wavelength of the frequencies of concern. The reverse also applies what frequencies should the equipment not emit so as to not cause interference to other equipment. The power of the signal plays an important part, the stronger the emission and susceptibility and more effective shielding is required. Lower frequencies can be shielded by single braid, medium frequencies double braid and higher frequencies should use foil or combinations of the two. The weak point on any cable system to an enclosure is the termination of the screen or shield. The above is the briefest description of the subject. EMI/RFI/EMC is a specialised field of engineering and expert advice should always be sought for designing efficient and effective systems.

The cable gland standard BS EN 50262 states that cable glands are EMI neutral, it is electrically passive until it is installed and then it is subject to the design of the earth/ground system and the ability of the installer to make the connection correctly. The design of the cable gland permits excellent connectivity and if done correctly will add to the shielding effectiveness of the system.