Shielded cable

Shielded Cable

	Email		Print
	Bookmark		Link

Shielded cable

A shielded or screened cable is an electrical cable

Cable

A cable is a large fiber or metal rope, used for hauling, lifting, or towing, or an assembly of two or more insulated electrical conductors, laid up together as an assembly....
of one or more insulated

Electrical insulation

An insulator, also called a dielectric, is a material that resists the flow of electric current. An insulating material has atoms with tightly bonded valence electrons....
conductors enclosed by a common conductive layer. The shield may be composed of braided strands of copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29.It is a ductile metal with very high thermal and electrical conductivity....
(or other metal), a non-braided spiral winding of copper tape, or a layer of conducting polymer.

Discussion

Ask a question about 'Shielded cable'

Start a new discussion about 'Shielded cable'

Answer questions from other users

Full Discussion Forum

Encyclopedia

A shielded or screened cable is an electrical cable

Cable

Electrical insulation

Copper

Faraday cage

A Faraday cage or Faraday shield is an enclosure formed by electrical conductor, or by a mesh of such material. Such an enclosure blocks out external static electrical fields....
to reduce electrical noise from affecting the signals, and to reduce electromagnetic radiation

Electromagnetic radiation

Electromagnetic radiation takes the form of wave propagation waves in a vacuum or in matter. EM radiation has an electric field and magnetic field component which oscillate in phase perpendicular to each other and to the direction of energy Wave propagation....
that may interfere with other devices. The shield minimizes capacitive

Capacitance

In electromagnetism and electronics, capacitance is the ability of a body to hold an electrical charge.Capacitance is also a measure of the amount of electric charge stored for a given electric potential....
ly coupled noise from other electrical sources.

In shielded signal cables the shield may act as the return path for the signal, or may act as screening only.

High voltage power cables with solid insulation are shielded to protect the cable insulation and also people and equipment.

Signal cables

By twisting two conductor

Electrical conductor

In science and Electrical engineering, an electrical conductor is a material which contains movable electric charges. In metallic conductors, such as copper or aluminum, the movable charged particles are electrons ....
s of a balanced-line

Balanced line

Transmission lines are generally unbalanced or balanced. Balanced lines are often operated with differential signaling. Balanced twin-lead is used for radio frequency signals and twisted pair for lower frequencies....
signal circuit into a twisted pair

Twisted pair

Twisted pair cabling is a form of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference from external sources; for instance, electromagnetic radiation from unshielded twisted pair cables, and crosstalk between neighboring pairs....
, some cancellation of inductive

Inductance

Inductance is the property in an electrical circuit where a change in the current flowing through that circuit induces an Electromotive force that opposes the change in current ....
ly-coupled noise is obtained. However, a metallic shield layer over the twisted pair

Twisted pair

Coaxial cable

Coaxial cable is a cable consisting of an inner conductor, surrounded by a tubular insulating layer typically made from a flexible material with a high dielectric constant, all of which is then surrounded by another conductive layer , and then finally covered again with a thin insulating layer on the outside....
is used at higher frequencies to provide controlled circuit impedance

Impedance

Impedance may refer to:*the ratio of the voltage phasor to the electric current phasor, as in**Electrical impedance, a measure of opposition to time-varying electric current in an electric circuit....
, but the outer tubular conductor is also effective at reducing coupling of noise into a circuit.

Applications

The use of shielded cables in security systems protects them from power frequency and radio frequency interference, reducing the number of false alarms being generated.

Microphone

Microphone

A microphone, sometimes referred to as a mike or?more recently?mic, is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal....
or "signal" cable used in setting up PA

Public address

A public address or "PA" system is an electronic amplifier system with a Mixing console, amplifier and loudspeakers, used to reinforce a given sound, e.g., a person making a speech, prerecorded music, or message, and distributing the sound to the general public around a building....
and recording studios is usually shielded twisted pair cable, terminated in XLR connector

XLR connector

The XLR connector is an electrical connector design. XLR plugs and jack s are used mostly in professional Sound recording and reproduction and video electronics cabling applications....
s. The twisted pair carries the signal in a balanced audio

Balanced audio

Balanced audio is a method of interconnecting audio equipment using balanced line. This type of connection is very important in sound recording and production because it allows for the use of long cables while reducing susceptibility to external noise....
configuration.

The cable laid from the stage to the mixer

Mixing console

In professional Sound reproduction, a mixing console, or audio mixer, also called a sound board or soundboard, is an Electronics device for combining , routing, and changing the level, Timbre and/or dynamics of audio signals....
is often multicore cable

Multicore cable

An audio multicore cable, or most commonly known as a snake is a compact cable, typically about the diameter of a coin, used in the audio recording and entertainment fields, which contains typically 4-64 individual shielded pair microphone cables all housed by one common outer jacket....
carrying several pairs of conductors.

Consumer grade microphones use screened wire with one central conductor in an unbalanced configuration.

Also see: High-end audio cables

High-end audio cables

High-end audio cables are claimed to improve the sound quality of high end audio systems but whether they actually do is hotly disputed. Since the audio signal passes through cables on its way from the source to the amplifier, or from the amplifier to the speakers, the cables will affect that signal....

Power cables

Medium and high-voltage power cable

Power Cable

Power Cable, Nebraska is a fiction town in United States used as a generic placename . It may have originated with Terry Pratchett, who dedicated Sourcery to its inhabitants, set a scene in Good Omens there, and made it the home of the publisher of Johnny Maxwell's encyclopedia, Universal Wonder Knowledge Data Printing Inc, in '...
s, in circuits over 2000 volts, will have a shield layer of copper or aluminum

Aluminium

Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....
tape or conducting polymer. If an unshielded insulated cable is in contact with earth or a grounded object, the electrostatic field around the conductor will be concentrated, resulting in corona discharge

Corona discharge

In electricity, a corona discharge is an electrical discharge brought on by the ionization of a fluid surrounding a conductor , which occurs when the potential gradient exceeds a certain value, but conditions are insufficient to cause complete electrical breakdown or electric arc....
, and eventual destruction of the insulation. As well, leakage current and capacitive

Capacitance

In electromagnetism and electronics, capacitance is the ability of a body to hold an electrical charge.Capacitance is also a measure of the amount of electric charge stored for a given electric potential....
current through the insulation presents a danger of electrical shock on contact. The grounded shield equalizes electrical stress around the conductor, diverts any leakage current to ground, and blocks capacitive current from flowing into objects (or persons) touching the exterior of the cable.

Shields on power cables are connected to earth ground. On high current circuits the shields must be connected only at one end, since induced current will flow in the shield. This current will produce losses and heating and will reduce the maximum current rating of the circuit. On very long high-voltage circuits, the shield may be broken into several sections since a long shield run may rise to dangerous voltages during a circuit fault.

Shielded cable

Signal cables

Applications

Power cables

See also

External links