Re: [LAU] ground loop hell

On Sun, Feb 08, 2015 at 08:08:23PM -0800, Len Ovens wrote:

> >Sometimes you really do have to be an a$$hole about that sort of thing.
>
> Just did the same thing today... "Can't this wait till after?"...
> "No, This is a safety issue." Funny we fixed two safety issues with
> one change as the cable went across 20 ft of floor to get to an
> outlet, so we got rid of a tripping hazard as well. Sometimes it
> just takes speaking up and doing it. Should have looked at it long
> time ago.

And that's the only right thing to do.

Re. putting 10 ohm resistors in the ground connection: if you
have two different ground voltages they are likely to be low
impedance (if not a good cable connecting them would remove
the problem). Assume you have 10 V difference and that the
impedance between the two grounds is 10 ohm as well. Then
we have 20 ohm total, and a current of 0.5 A. That's 2.5 Watt
in your 10 ohm resistor. Which means it will first turn red
and then and self-destruct in a puff of smoke. Unless it's a
really big resistor.

The only solution if you can't have a common ground is to use
transformer isolated balanced connections, this allows you to
disconnect ground at one end and still have a signal.

Without the transformer isolation you could easily blow up
either the output or the input, or both.

Ciao,

-- 
FA
A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)
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