Coil scoping

To: tesla-at-pupman-dot-com
Subject: Coil scoping
From: "LWRobertson" <LWRobertson-at-email.msn-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Wed, 02 Feb 2000 05:26:05 -0700
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Hi,

I finally got to scoping my coil to see if it was possible
to determine where on the waveform the breakout first
occurs. I'm using a Tectronix 400 Mhz 2467B with an
image intensifier to help out with transients.

I used a 3 inch piece of wire connected to a 10x scope
probe, held three feet from the toroid, radially. I set the
power so it was firing regularly at about 2 PPS, and
would not break out from the toroid. I brought a ground
nearby to observe breakout, at about 8 inches of spark.
I also think it's time to get one of Terry's probes for this
sort of thing.

With no breakout I observed three envelopes before
quench, then the long ringdown, as usual. With spark
breaking out the situation became more interesting.
The spark was quite obvious as the amplitude decayed
dramatically in a very short time.

For a few hundred nanoseconds after the spark a 34 Mhz
signal decayed, spurious inductances from the wiring,
probably. Then a long ringdown at the secondary frequency
at low amplitude. In every case the spark occurred after a
negative excursion of the main resonance at 108 kHz,
but right at zero amplitude.

I don't know how to interpret this. I will try to get a current
probe on the ground line to see how that correlates with
the spark.

LR