[ntp:questions] GPS 18 LVC (Ground Wire Question)

Alby google at empire.org
Wed Mar 17 03:36:29 UTC 2010

On 16 Mar, 15:03, unruh <un... at wormhole.physics.ubc.ca> wrote:
> On 2010-03-16, E-Mail Sent to this address will be added to the BlackLists <N... at BlackList.Anitech-Systems.invalid> wrote:
> > Alby wrote:
> >> (Garmin GPS 18 LVC, 5m).
> >> So can I assume the extra thin black wire is just an
> >>  additional ground wire?
> > One black wire is the power common,
> >  another black wire is the data common,
> >  the third black wire is a shield drain.
> What is a "shield drain" and how do you know this? It is just off the
> top of your head, or is there some more authoritative source for this
> info?
> (anyway, it sounds like there is nothing to prevent you from tying all
> grounds together, unless the power comes from a source with a separate
> ground from what the data ground is tied to, which could give bad ground
> loops. In that case I would assume that you would tie the shield ground
> to the power ground.

 I think I figure it out.  The extra black wire on my GPS Unit is
because my
model is a Garmin GPS LVC, 5m. The typical unit is a 3m. Meaning my
cable length
is 5 meters long, while the standard is 3 meters. Given the extra
distance in my
cabling, the additional black wire is performing the function of an
electromagnetic shield.
The poster who mentioned "drain wire" jogged a memory.

 drain wire definition - telecom
A wire wrapped around or part of a shield within a cable that reduces
the resistance from any point on the shield to ground. A drain wire
serves to complete an electrical circuit from the shield, thereby
carrying extraneous electrical noise to ground and away from the
circuit or system the shield is intended to protect. See also ground,
ground wire, and shield.

More information about the questions mailing list