1.What is the shield wire?

Shielded wire is a transmission cable that uses a network of braided wires to wrap the signal wire. The conductor wrapped around the conductor is called shielding wire, and the wrapped conductor is called shielding layer, which is generally braided copper network or (aluminum). The shielding layer needs to be grounded so that external interference signals can be imported into the earth by this layer to avoid interference signals entering the inner conductor and reduce the loss of transmission signals.

Shielded cable shielding layer is mainly made of copper, aluminum and other non-magnetic materials, and the thickness is very thin, far less than the skin depth of metal materials using frequency (the so-called skin effect refers to the distribution of electric current in the conductor cross section along with the rise of frequency distribution of conductor surface, the higher the frequency, the smaller the skin depth, the higher the frequency, electromagnetic wave penetration weaker). The effect of the shielding layer is not mainly due to the reflection and absorption of the electric field and magnetic field by the metal body itself, but due to the grounding of the shielding layer. The different forms of grounding will directly affect the shielding effect.

2. the type of shielding wire

It mainly includes bare wire, electromagnetic wire and electrical insulation wire, power cable, communication cable and optical cable. Wires and cables refer to materials used for electric power, communications and related transmission purposes. There is no strict  between "wire" and "cable". Usually the number of cores, small product diameter, simple structure of the product is called wire, no insulation is called bare wire, the other is called cable; Conductor cross-sectional area is larger (greater than 6 square millimeters) known as large wire, smaller (less than or equal to 6 square millimeters) known as small wire, insulated wire is also known as cloth wire.

Wire and cable mainly includes bare wire, electromagnetic wire and electrical electrical insulation wire, power cable, communication cable and optical cable. Cables include power cable, control cable, compensation cable, shielded cable, high temperature cable, computer cable, signal cable, coaxial cable, refractory cable, Marine cable and so on. They are made up of wires that connect circuits, appliances, etc.

Normal: insulation layer + shielding layer + wire. Advanced: insulation layer + shielding layer + signal wire + shielding grounding wire.

3. Application of shielded wire

The shielding layer generally needs to be grounded. The function of the shielding wire is to isolate the electromagnetic noise source from the sensitive equipment and cut off the transmission path of the noise source.

Shielding is divided into active shielding and passive shielding. The purpose of active shielding is to prevent the noise source from radiating outward. It is the shielding of noise source. The purpose of passive shielding is to prevent the sensitive equipment from being interfered with by noise sources. It is the shielding of sensitive equipment.

The shielding layer of the shielding wire does not allow multi-point grounding because different ground points are always different and there is a potential difference between each point. Such as multi-point grounding, the formation of current in the shielding layer, the formation of current induced to the wire, the formation of interference induced to the signal wire, not only can not play the role of shielding, but also the introduction of interference, especially in the occasions where the frequency converter is used more, the interference contains a variety of high-order harmonic components, causing greater impact, should pay special attention to.