
Understanding, finding, and eliminating ground loops (2003) [pdf] - PascLeRasc
http://web.mit.edu/jhawk/tmp/p/EST016_Ground_Loops_handout.pdf
======
mojomark
I actually read this document recently for my work on grounding equipment on
ocean going vessels. Surprisingly, there is very little in Mil-std-1310 (1)
about ground loops on ships. Ships are interesting from a grounding
perspective because your grounds are generally attached to the steel hull
which represents the "common electrical potential".

People get confused when comparing ships to land based (e.g. building) grounds
in which two or more grounds in, say a building's earthen foundation, could
have very different potentials for a variety of reasons and thus ground loops
can be present in shielded cables grounded at both ends. On ships, however,
unless there is some strange disconuity, the ship's hull is a common potential
and generally no ground loop will be generated, so you can generally have a
doubly grounded cable with little risk of organic noise.

1.)
[http://quicksearch.dla.mil/qaDocDetails.aspx?ident_number=36...](http://quicksearch.dla.mil/qaDocDetails.aspx?ident_number=36209)

------
benji-york
Related: [http://www.rane.com/note110.html](http://www.rane.com/note110.html)

------
crispyambulance
That's a useful read!

One thing I've always wanted to know: Where is the actual "ground rod" in a
building/residence? How do I find it? I've assumed it was just the water pipe,
but now I am not sure.

Also, don't these rods get corroded to oblivion after decades in the ground
from electo-chemical reactions?

~~~
twothamendment
Above, someone mentioned rebar in the foundation. That is a Ufer Ground. In
places with very dry soil you can pound a stack of ground rods into the earth
and still not get a good ground. Ufer figured out that concrete in the
foundation provides a good ground.

[https://en.wikipedia.org/wiki/Ufer_ground](https://en.wikipedia.org/wiki/Ufer_ground)

5 years ago I built my house and did my all my electrical, I needed a Ufer
ground in the foundation and 2 ground rods near the meter. Being a newer area,
water lines were plastic.

------
jhawkinson
Just in case it was not obvious from the URL (/tmp/p), this is not a durable
URL and not guaranteed to last there.

------
chiph
I used to be involved in car audio in the late 90's, and the people involved
came up with many of these solutions via trial & error.

\- Have a central grounding point - a steel car body has higher resistance
than copper wire so using multiple ground locations will introduce voltage
differences.

\- Use a large gauge _stranded_ wire for your ground.

\- Use the same gauge wire for the ground as you did for the power wire.

\- Keep wire runs short.

\- Use twisted-pair wire for audio connections.

So for a multi-amp system, you'd run a large gauge wire from the battery
positive to a distribution block, and from there to the head unit and amps.
The ground from the head unit & amps would use the same diameter wire and be
run to a central point. The ground strap from the car body to the battery
negative post would perhaps be upgraded to the same diameter as the positive
wire.

~~~
janci
These are just the misconceptions the article talks about.

~~~
chiph
I suggest you look at my list and read the article again.

He is using ground loop isolators because of the length of his cable runs. In
a car, that's not a problem as anything over 3 meters would be rare.

Single point grounding makes sense, because as I said, steel is a worse
conductor than copper, so you'll end up with a voltage difference between your
grounds (from each to the battery) if you use more than one.

So far as twisted pair, he strongly suggests using them to provide shielding
against magnetic induced noise. They also provide good shielding against RFI -
remember you've got 4-8 spark transmitters running at 900 to 5000 rpm interval
in the engine.

And using the same size wire for both power and ground makes sense because
different gauge wire has difference resistance.

------
alricb
See also: [http://www.jensen-transformers.com/application-
notes/](http://www.jensen-transformers.com/application-notes/)

The author, Bill Whitlock, is the president of Jensen Transformers, makers of
high-end audio transformers.

------
valenciarose
Thanks for posting.

