On Apr 30, 8:02 am, John Durbin wrote:
You are wrong... look at it from the perspective of the resistance of
the car chassis as a ground path vs. the piece of wire you used. Just
how big a gauge do you think would be needed to equal the car's chassis?
John, don't forget that the "chassis" isn't always one big piece of
metal. If you choose a ground point on a welded-on member of the
chassis, you may very well run into conductivity issues. I've
personally installed systems in vehicles where the simple act of
moving the system's ground point radically impacted the system (i.e.
either eliminating or introducing noise). As far as cross-sectional
area goes, let's not forget that electricity will travel the path of
least resistance....it's been a while since my studies as an EE, but I
don't think it's safe to assume that the entirety of the chassis is
not going to be used as the path from source to sink--if we assume a
superconducting chassis (i.e. no resistance), that current is going to
flow in the shortest line possible, right? Which is not to say that
the electrons are going to be scattered all over the chassis, but
rather more or less concentrated in a "stream" of sorts. Isn't that
correct, or do I need to go back to kollege? Even if that isn't the
case, the notion that "anywhere on the chassis is fine" is not
supported by empirical results of DCR tests that I and my colleagues
of old have performed on vehicles which demonstrated that different
spots on the vehicle's chassis can, and often do, present differing
levels of resistance back to the negative terminal of the battery.
Note that this isn't to say that all vehicles display this phenomenom,
nor does it mean that if one grounds all components to a single point
on the chassis that noise will never creep in--there are more
variables that can introduce system noise than you can shake a stick
at. What I am saying, though, is that my experience has shown that a
system with multiple ground points is likely to be more susceptible to
ground loop issues, and a system with a single ground point is less
likely to suffer from the same ailment.
I also don't agree with the gold thing, either. True, gold doesn't
oxidize significantly and cause problems that way, but having a few
microns of gold plating is not going to make a significant difference
in terms of the malleability of the O-ring terminal and thus give it a
better connection. Most O-rings are made of copper--which is malleable
in its own right and incidentally is a better conductor than is gold
when clean (
http://www.wisetool.com/designation/cond.htm). The O-ring
terminals I used back in the day were made of copper and were
electrostatically plated with some other relatively inert metal
(presumably aluminum)--and they conducted just fine thank-you-very-
much....and without costing an arm and a leg.
-dan