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In Reply to: Part 2: Ground is the wrong term today. posted by Ron Oehlert on April 26, 2007 at 14:48:18:
Ron>> The term *ground* with regards to electronic circuts
>> actually refers to circut Common return.Not in any circuit I have seen
in over 30 years as a technician.
Ground is EARTH ground on every circuit
I have worked on.>> With correct terminolgy, there then is no
>> such thing as a floating ground.Circut Common Return is floating, whenever
circuit current is flowing it increases
and thereby is no longer Earth ground
and is therefore floating.
That is why anything with a metal case
needs an three wire plug by law.
Also you can't recommend referencing your signal ground
to AC common and you don't recommend referencing them
to Earth ground - floating ground is all that's left.>> Signal or circut Common should NEVER have a
>> direct connection to AC Mains; only via the
>> chassis lest SAFETY be compromised.Circuit Common should never have a direct connection
to AC Mains ground inside your equipment is correct.
They are connected at the box but if you do this then
you are making your connection as an alternative
grounding route for the other devices on your circuit
and corrupting the safety providing earth ground.
But since the signal ground produces no significant current
and is using it only as reference NO safety is compromised.>> So why refer to any electrical connection
>> in such circuts as a *ground*?Because earth ground is the BEST reference
whether you are talking AC or signal.
I ground ALL my equipment without problems.
I actually run a "new" ground route usually
from a convenient water pipe nearby.
Common/return and ground are the same point
at the incoming box but are different soon after
and are more different the further you get away
from the box because accumulated resistance and
more devices drawing current.>> absolutely NO direct Earth Ground connection
>> is neccessary for automobile ...On purpose because the automobile would be
susceptable to lightning strikes.
They found that out the hard way.
As well as why to have a negative ground.
Positive grounded vehicles rust very quickly.
Follow Ups:
Please notice that virtually all inmates here write ground when refering to circut Common. You do so yourself, see link below:
RonBecause I connect the circuit ground to earth ground.
So they are the same point sir.Circuit ground and AC common are definitely different.
Do not connect AC common to ground.
Do connect circuit common to ground.
Just because you do it that way does not make it SAFE for others.
RonGrow up please - you're gotcha game is so juvenile.
Just because I can take a shock does NOT mean anything.
ALOT of people run seperate grounds,
some even run dedicated power feeds.
Nothing unsafe about this.
needs an three wire plug by law."I don't understand all the electrical laws in every state and region and every country as well.
But, I have a CD player that has an all metal case and has the obligatory three wire plug, but it only uses hot and neutral inside the box. The ground connection is unconnected. The manufacturer passes the law by double insulating the mains on the wires going to the power transformer primaries even with a metal case. They just add another layer of plastic insulation over the standard mains wire. Apparently, this is good enough by today's electrical codes.
The output signals of the CD player appear to be just floating. I guess the outer box is connected to circuit common. When connected to an amp that has its circuit common connected to Earth ground, then the whole system is shielded by ground potential.
It sounds best to have only one box grounded to Earth ground to avoid ground loops. Apparently it can still be done legally. My CD player is an Ayre, made today in the USA, and I know they know what they're doing.
KurtI know people have ground loop problems.
I always cure them with better grounding
on each and every componant.
The idea that your ground reference is
provided through an interconnect seems to me
as a problem waiting to happen.
Maybe that's just me.
I like everything grounded well.
For someone who is so sure of himself... you say a lot of really silly things.Have a nice day.
HenryIf EVERY componant was PERFECTLY grounded then
there wouldn't be any ground loop problems.
Not so silly if you think about it.DanL
"There is no such thing as Ground."That is an axiom that is posted on the cubicle of one of our star analog design gurus where I work.
What does it mean? It means there is only a mere approximation of ground. Ground is an illusion and there is no perfect ground, ever.
It's also unfortunate that Henry sometimes chooses not to expound on his knowledge, because he does indeed know a lot about what he's talking about.
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