grounding

[ndorado]

need an answer to this question. in a 12 volt system, like on a boat, when you connect the positive and negative to your bus bar, is the negative considered the ground and if so then why do some units come with another ground wire?

[Birdman]

I'll assume you are referring to the "Sheild" wire as the "2nd ground".

The ground is the return line, which completes the flow of electricity. The Sheild wire is a coating a wire around the other wires (whatever they are) that does a few things. One is ussually ground the case of the electronic device (light, gps, whatever), so if something shorts, the electric follows the path of the "sheild" wire rather than down your hand. Another thing it does is pick up and get rid of some of the rf noise that is both leaving the wires and possibly coming into the wire (from another close by device.

That answer yoru question?

Birdman, Capt of

Scout Abaco 280 Click here!

[sailfish272]

Some units, particularly those with a metal chassis will also have a chassis ground. This is usually a small screw in the back with the ground symbol next to it. Connecting this will not affect performance, but will provide a path to ground in the event of an internal short. If it is not coneected, the next lucky person to touch the chassis will provide the path.