[simpits-chat] Wire length question

Ben Jones simpits-chat@simpits.org
Thu, 10 Jul 2003 14:35:28 +0800

----- Original Message -----
From: "Joseph Fagner" <falcon4@sbcglobal.net>
Subject: RE: [simpits-chat] Wire length question

>> Now, I did do one other thing when I connected these guys, I wired in the
> signal ground with the shield wire mesh chassis ground.  Am I going to
> problems with this?  I have found some cables that do this and some that
> don't.  There is a bare wire in contact with the mesh shield and some of
> cables I have seen (i.e. taken apart) have this bare wire attached to the
> signal ground (which is essence makes a connection between the mesh shield
> and the signal ground).  This question is for anyone out there.
> Jay


i cant comment on the max length of usb cables , as i have no experience
with "making"any

and i cant comment on whever to ground the earth wire"shield wire" to the

but with my experience in the electrical industrial area , if you ground the
shield wire to earth only ground to earth at one end !
if both ends of the cable are shielded , you are creating a low resistance
circular parth throught  the cable down to earth and then back through the
cable , this can be verry bad in certain occasions , due to "eddy currents"
running through the cable or shield wire  which are induced by near by
electrical cables..... this can often degrade the performance and the signal
more than if you dont shield the cable at all..

having said that i assume you wont have any huge cables running in close
proximity to your usb cables that carry ang great amperage in you pit
so to be safe only ground one end of the shield core to earth usally at the
computer side and leave the other  end of the wire not connected to earth ,
either trim it back to flush with your insulation around the cables or leave
about 10mm of shield hanging out and heat shrink.

hope this rambelling helps