On 16 Mar, 15:03, unruh <[email protected]> wrote: > On 2010-03-16, E-Mail Sent to this address will be added to the BlackLists > <[email protected]> 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. http://www.serialphy.com/multi-conductor-cable.bmp _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
