Why you need to use the shielded cable?
The shielded cable can protects the signal from external interference. As we know, Cables can be a main source of transfer for EMI, both as a source and receiver. As a source, the cable can either conduct noise to other equipment or act as an antenna radiating noise. As a receiver, the cable can pick up EMI radiated from other sources. A shield works on both. The cable with shields ability can maintain signal integrity in a noisy environment, such as airport, factory etc.
Different type of shielded cable
There are three most common shielded cable, Braid Shield ( e.g coaxial cable), Spiral Shield (e.g some audio cable), Foil Shielding (e.g some coaxial cable)
It is the most common method of shielding. A cable that is shielded by crossing layers of individual metal stands (normally are copper or aluminum metal) over a cable core or an insulated conductor.
The spiral shield consists of wire (usually copper) wrapped in a spiral around the inner conductor wire.
It consist of aluminum foil laminated to a polyester or polypropylene film. The film gives the shield mechanical strength and bonus insulation. Foil shields provide 100% cable coverage, necessary for electrostatic shield protection. Because of their small size, foil shields are commonly used to shield individual pairs of multi-pair data cables to reduce crosstalk.
The feature of different shielded cable
|Braid Shield||Braid shields provide superior structural integrity,e ideal
for minimizing low frequency interference and have lower dc resistance than foil. Braid shields are effective at audio, as
well as FR ranges. Generally, the higher the braid coverage, the more effective the shield.
|Braid shields are generally bulkier and heavier than other shields and, in some cases, harder to terminate because the
braid must be combed out and pigtailed.The trade-off
between cost and braid coverage must be considered.
|Spiral Shield||The Spiral Shield provide superior flexibility, requires less copper, much faster and cheaper to manufacture, and is quicker and easier to terminate than a braided shield. They
are best choice for audio cables.
|Spiral shields are not effective above the audio frequency range due to
the coil effect produced by the inductance or served wire strands.
|Foil Shield||Foil shields provide 100% cable coverage, necessary for electrostatic shield protection,have less weight, bulk and cost less than spiral or braid shields and are generally more effective than
braid shields in FR ranges.
|Foil shields have a shorter flex life than spiral or braid, and using the foil shield include higher de-resistance and lower mechanical strength than braid or spiral shields.|