In my opinion, letting the cable insulation touch the probe body is never a
good idea. I always try to "shim" the cable and probe in order to center the
cable within the probe opening. The trick is to keep the shims outside of
the probe. A good trick is to make a "V block" out of wood, with a deeper
center notch for the probe body. This insures good radial and axial
alignment (for consistency) and also prevents the probe body from touching
the ground plane.
Scott
-----Original Message-----
From: Jim Eichner [SMTP:[email protected]]
Sent: Monday, June 21, 1999 1:10 PM
To: EMC-PSTC
Subject: RE: Current probe problem
In his write up of the problem, Doug writes
"If possible, current probes should be positioned on the measured
cable
so as to minimize the potential between the cable and the current
probe
body. This usually means locating the probe near the ground/chassis
end
of a circuit."
Following a tip from someone on this forum quite a while ago, I have
observed significant variation in the spectrum of noise along the
length
of a cable. I have started doing my cable current measurements by
sliding the probe over the length of the cable, with my spectrum
analyzer in max hold mode. I assume I get a "worst case sweep" by
doing
this, as I pick up the worst of everything at any position on the
cable.
Following Doug's advice above, or any instance of using a current
probe
in a single fixed position, could result in the probe being
positioned
right at a null for a frequency of interest, sending you on a wild
goose
chase looking for some other source.
Does Doug or anyone else have similar experience or a better way to
overcome the problem?
Regards,
Jim Eichner
> Senior Regulatory Compliance Engineer
Statpower Technologies Corporation
[email protected]
http://www.statpower.com
Any opinions expressed are those of my invisible friend, who really
exists, but can only be seen by my dog. Honest.
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