Engineering Definitions
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Braid. A fibrous or metallic group of filaments interwoven to form a protective covering over one or more wires. When used as a conductor or shield the braid is metal.

Metal Braid Usage in a Coax Cable
Dual Braid Cable

Metal Braid. [Cable Shield] Flexible wire constructed of small size strands in tubular form. Used for shielding or connections where constant flexing is required. A wire braid may also be used as a Drain Wire. Also refer to a Wire Braid Graphic.

Metal braid shielding can either be woven directly over a core or obtained in pre-braided form and installed by sliding it over the wire bundle. To prevent potential damage (cold flow) of the underlying wire insulation, a separator (e.g., a tape) may be applied over the wire bundle to give the wire continuous protection. Pre-woven braiding shall be tightened down to contact the wire bundle. Copper braid is the most effective RF shielding. Copper-clad steel-core wire, woven into a flat braid, is also effective shielding material. On RF signal cables, both the inner conductor and outer conductor braid should be electrically continuous.

The cable may have one or more Wire Metal Braids. The two most common styles are a Single-braid coaxial cable [Single shield] or a Double-braid coaxial cable. [Double shield, more expensive]. However in some cases the cable with a dual wire braid may not have the conductors separated by an insulation tape. That is, if two individual metal braids are lying side-by-side than they are considered as a single conductor. While two individual metal braids that are separated by an insulating tape are considered two separate conductors. The diagram above shows an outer braid and an inner braid, both considered as the outer conductor of a coaxial line. In most cases the braid would be carrying the signal return or ground.

Metal Braid Usage in a Triax Cable
Dual Braid Cable

If the different metal braids are not making electrical contact than the cable would be considered a triaxial cable instead of a coaxial cable. The braid could be separated by another dielectric inner layer, as in the same material used for the dielectric core, or by an insulating tape. As an example the barrier tape could be a 0.001 thick polyester tape that is wrapped with a 50 percent overlap. Some cables use multiple wraps of barrier tape, that is one wrap of tape with a 50 percent over-lap and than another wrap of tape over that [also with an over-lap].

Wire braid is usually specified using a wire gauge [AWG], although the braid does not have to be copper or tin-coated copper. The percent coverage is also specified, the higher the coverage the better the shielding. RG58 cable, for example, has a braid coverage of over 90 percent and uses a number 36 gauge braid of tinned copper wire.

Braid Termination socket
Braid Washer Termination

Note that the wire hole for terminating the braid in the graphic above is not that large. So depending on how the braid is stripped back from the cable, only a portion of the braid will be able to make a mechanical connection via the wire-hole. So care should be taken when removing the wire braid from the rest of the cable to keep it as small as possible.

If the conductor or shield is a metal foil than it would not be considered a braid.

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