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Suggested methods of shield termination without the use of a by csgirla

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									Tips on terminating cable shields to enclosures without a connector.

D. A. Weston                          bkupd.doc                      25-1-2002

The simplest and one of the most effective techniques for shield termination is the use of
a ring bolted inside the enclosure. The ring is used to clamp the shield of the cable which
penetrates through an aperture in the enclosure wall. As the ring clamps the shield around
180° no significant apertures exist and the shielding is very high. Figure 1 illustrates this
technique.




                                              Fasteners


                                                                            Cable
        Cable
                                                                           Shield
        Shield                                                             Clamp
        Braid



                                                                     Cable

       Inside surface of enclosure


Figure 1 cable clamped by a ring

Another form of shield termination uses a compression fitting, similar to the fitting used
in plumbing (in commercial applications we actually use the plumbing fitting). Here the
shield is clamped behind a collet using nuts and the inside of the fitting is also held
against the enclosure wall by a nut. Figure 2 illustrates this technique.




                                                                                            1
                                   Cable
                                   shield
                                    braid

                                                                        Shielded cable




  Nut                                    Collet            Nut




                        Enclosure wall
                          or bulkhead


Figure 2 Collet used to clamp shield in a compression fitting

The final method is less satisfactory as it is easy to leave a gap between the end of the
shield and the aperture in the enclosure which will compromise the shielding. However
it is fairly simple to make and if properly installed will typically achieve adequate
shielding. Figure 3 illustrates this technique.




                                                                                            2
                                 Cable clamp

                                            Cable shield braid


                                                                 Cable



                            Enclosure wall




Figure 3 Cable clamp screwed into enclosure wall.




                                                                         3

								
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