Not familiar with the probe. Sounds like "punch through"
voltage is appearing. Twisting removes current loops and
shielding removes "punch through" voltage.
Difficult to offer much more advice without "seeing" the
setup. Or, someone else fought this battle and knows
instantly what it is.
- Robert -
On Tue, 23 Mar 2004 13:13:18 -0600
"Derek Walton" <[email protected]> wrote:
> To monitor the signal I'm using a 100 MHz Diff scope
> probe. I've twisted
> the sense leads together to minimise coupling in that
> loop.
>
> Z in the circuit is really low....
>
> Mind you, I have made no provisions for the wiring that
> charges the
> energy ctorage cap. Maybe i should better tie thoese
> down. Since I'm
> using a "change over" relay, I wonder if what I'm seeing
> is to do with
> the cap ESR being too low.... I'm using Mica Caps.
>
> The spike I refer to looks just like the spike on an ESD
> waveform in the
> IEC standards.
>
> Cheers,
>
> Derek.
>
> robert Macy wrote on 3/23/2004, 1:03 PM:
>
> > 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" <[email protected]> wrote:
> > >
> > >
> > > -----Original Message-----
> > > 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
> > >
> >
>
> --
> Derek N. Walton
> L F Research
> Poplar Grove, IL 61065, USA
>
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