I tend to agree with Robert since, I too, have chased my tail only to find out
the bogus signal was an artifact of the test equipment rather than the UUT.
Even if you are using a differential probe it still may be a common mode
signal that is coupling in. Most scopes have a cmrr of only 12 to 20 db.
This is not nearly enough cmrr if you are dealing with high voltage.
In another vain the offending glitch will not be caused by stray inductance if
it is at the leading edge. The L/R time constant will delay the glitch toward
the trailing edge of any pulse. Sounds like capacitive leakage or EMI if not
a test equipment problem to me.
Fred Townsend
robert Macy wrote:
Make certain the signal is real and not an artifact.
I once chased a signal for four hours before I discovered
it was the scope ground "bouncing" ..well that, and other
stuff. Differentially, the signal WAS NOT THERE.
- Robert -
Robert A. Macy, PE .. [email protected]
408 286 3985 . . . .. . . fx 408 297 9121
AJM International Electronics Consultants
101 E San Fernando, Suite 402
San Jose, CA 95112
On Tue, 23 Mar 2004 09:57:30 -0800
"Price, Ed" <mailto:[email protected]> <[email protected]> wrote:
From: Derek Walton [ mailto:[email protected]]
Sent: Tuesday, March 23, 2004 6:53 AM
To: [email protected]
Subject: Tweaking a transient Generator
Good day all,
I've been developing a damped sine generator to perform
the DO-160 lightning
test, and have had some reasonable success. However (
there is always a
gotcha ), the leading edge of the 1 MHz ring wave has a
very short ( around
10 nS ) spike on it. I have tried a number of things to
kill the spike, but
to no avail. Does anyone have suggestions on what causes
this, and ways to
eliminate it?
I have strived to keep stray inductance small, very
small, maybe too
small.....
The switch is a high voltage vacuum relay.
--
Derek N. Walton
L F Research
Poplar Grove, IL 61065, USA
Derek:
Why not put up a schematic, plus a couple of
multiple-angle photos, and give
us a link so we can see what you are doing?
Ed
Ed Price
[email protected] WB6WSN
NARTE Certified EMC Engineer & Technician
Electromagnetic Compatibility Lab
Cubic Defense Applications
San Diego, CA USA
858-505-2780 (Voice)
858-505-1583 (Fax)
Military & Avionics EMC Is Our Specialty
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