Cable shields are shields for electrical cables that contain insulated conductors in a standard conductive layer. This shield can be made of woven copper filaments (or similar metal), a helical copper strip or some other conductive polymer.
Shielded cables are usually thicker and stiffer than non-shielded cables and also require extra care when working with them. Shielded cables are often found in industrial settings and facilities where other adjacent equipment is likely to cause electromagnetic interference (EMI).
Shielded and twisted cables do not have internal protection to reduce EMI. Instead, they are designed to cancel EMI using a pair of twisted wires. These cables are lightweight and thin, making them ideal for indoor use in local offices for local area networks or network cable systems. They are also less expensive than industrial cables. However, they are not always suitable for industrial applications, such as where more energy is required or heavy equipment is used regularly.
What is the purpose of cable shield?
Shielded cables are used to protect the data transmitted over the cable from damage due to EMI exposure damage in data centers, industrial settings, offices and other settings such as computer technology, electrical equipment or electronics Heavy use is common.
EMI is generated by an external source that affects the electrical circuit through electrical connection, conduction or electromagnetic induction. EMI malfunction can reduce or even shut down the circuit. Wherever there is a data path, these effects can range from increasing the error rate to complete data loss. Both natural and man-made resources (man-made) can generate variable currents and voltages that trigger EMIs. Combustion of vehicles and mobile phones are prominent examples of EMI artificial resources. EMI natural resources include electrical storms and the sun.
EMI typically disrupts AM radios, televisions, and cell phones.
Shield in shielded cables reduces the volume and intensity of electrical noise and reduces its effect on signals and transmission, while reducing electromagnetic radiation.
Foil and woven shield
Foil and woven shielded cables are two common types of shielded cables for industrial use. The foil shield consists of a thin sheet of copper or aluminum. This “foil” is usually attached to a polyester carrier to increase the strength of the cable. This type of shielded cable, also known as a “strip” shield, provides 100% protection of the conductor wire wrapped around it. No EMI can penetrate from the environment. However, because the foil inside the cable is so thin, it is very difficult to work with these cables, especially when using connectors. Most of the time, the drain wire is used instead of trying to completely lower the cable shield.
The second method used to protect the cables is weaving. Woven shielded cables use woven copper wire mesh. Woven shields have less coverage than foil shields but are much more durable. This knot creates a low ground resistance path and is very difficult to terminate when using the connector. Woven shields generally protect between 70 and 95% of the EMI, depending on the strength of the knot. Woven shields are more practical than foil shields because copper is more conductive than aluminum and because they are less prone to internal damage. Woven shielded cables are heavier and more expensive than strip shields because they are more durable and provide better performance.
Depending on the work environment, one type of cable may take precedence over the other. Some workplaces only need foil shielded cables, while they may need woven mesh shielded cables. Other works require a combination of cable types. Coil spiral cables should be used in places where the cables are frequently bent and moved. In areas where the cable may not move often but is exposed to pressure or impact, braided cables are often best. In environments where the cable is not expected to be disturbed by workers, machinery or other agents, foil protection is appropriate.
In all cases, the protective cables must be properly grounded to ensure the safety of workers and equipment.
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