[SI-LIST] Re: How to Measure Ground Noise
- From: "Pratt, Gary" <gary_pratt@xxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Fri, 8 Apr 2005 02:31:32 -0400
I suspect you are actually measuring the common mode ground current
coupling of the scope (plus the radiated energy passing through the loop
of the probe ground wire). See if your results change if you float the
scope power with a good medical isolation transformer (at your own
risk), or wrap the power cord many times through a good torroid, or wrap
the ground cable around the tip of the scope probe (to reduce the loop
area). =20
If you see a dramatic change, you will know your measurement reflects
more of whats going on in your measurement environment than what is
going on in your PCB. =20
Gary
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of ospyng
Sent: Wednesday, April 06, 2005 1:23 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] How to Measure Ground Noise
hi,
I was taught to measure ground noise, by having the ground of the probe
connect to ground TP of the board and the tip of the probe measuring the
same TP.
is this the correct where? and Why?=20
is it because of the ground cable (3 inch) cause a loop, therefore the
reference and the tip of the probe has a different voltage?
thanks
pyng
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=20
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