RE: [CAD_CAM_EDM_DRO] Re: Proper size of capacitors for transient suppression?

Jan:

I understand that the ground is "differential" to the signal lead, but a
differential input can only CANCEL what is "present" on the 2 lines. Induced
noise is cancelled by the input circuitry seeing the same signal on BOTH
lines, and taking the difference(or inverting one and adding them-same
thing), which should be "zero".

If the ground lead is grounded, and not tied to an input, then any noise
induced in it should be(at least partially) shunted to ground, and so will
not appear at the input circuitry. I guess that would only be 100% true with
a zero-impedance ground-kind of hard to achieve in the real world, huh?

I guess if the noise actually DID modulate the ground that appeared at the
input circuitry, the "non-differential" circuit would "pass" that modulated
ground through to it's output stages, and it "might" make it's way to the
next stage in the circuit-just thinking out loud here.

And no, I'm not remembering what an instructor told me-that stuff pretty
much disappeared in the haze induced in MY ground by whatever I was
ingesting back when I was in college. I have had many experiences(some good,
some bad, but almost all ultimately successful) in wiring and
troubleshooting large audio systems to make them work right, after trying it
the "right" way. I know that if you "Simulate" a balanced line by tying an
unbalanced audio output ("+" and "gnd") to a balanced input ("+" and
"-")using a twisted pair, with an overall shield, you CAN get some
observable results as far as noise reduction-but I have never measured it,
and don't know "why" it works.

Andy Wander
Verrex Corporation


-----Original Message-----
From: JanRwl@... [mailto:JanRwl@...]
Sent: Wednesday, May 12, 2004 11:14 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: Proper size of capacitors for
transient suppression?

In a message dated 5/12/2004 8:37:13 PM Central Standard Time,
awander@... writes:
I am curious to know if you or someone else on this group has actual
experience using this technique, and can say that it actually makes a
difference to run a twisted pair with one side of the pair grounded.

In theory, it should not work-but heck, I know that theory doesn't always
explain everything.

Andy: This is VERY common to control EMI in motor-circuits! The "ground"
lead IS "differential" to a signal-line, when there is no negative
mirror-image
of a positive signal, isn't it!

WHAT theory? Are you remembering something some EE instructor told you?
Never forget: Those who CAN, do; those who CAN'T, teach!


[Non-text portions of this message have been removed]



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