[TCML] Oscilloscope methods for showing Ringdown
follies at ntlworld.com
Thu Mar 12 05:06:23 MST 2009
In reply to DC's idea I forget to mention that I had already tried running
the coil at low bps on the Variac. I can get it to run on 50v (20% power)
when it fires at the rate, and also sounding like, a machine gun from a
World War 2 film, and still with a healthy spark.
Five or six bps? It's very difficult to tell without recording the sound
and analysing the waveform. Anyway the trace from the individual firings is
so quick that the scope barely shows it - unlike a storage scope would. So
the one-shot mode I think will fail, but I have seen some HV diodes on Ebay
that I'll try.
The scope's tube is rather tired as a faint 'quick' trace can be hard to see
on max brightness. The gap is static as Gary guessed so syncing to the mains
won't work. I am altering my voltage divider to attempt to get a low enough
signal to allow the SG to do the triggering - should be interesting. Has
anyone managed that and still left the scope working?
I could do with a duel channel model really, so the SG trigger idea might
mean I have to actually get one (plenty of Tek 465's on Ebay usually)
From: Lau, Gary [mailto:Gary.Lau at hp.com]
Sent: 12 March 2009 00:53
To: Tesla Coil Mailing List
Subject: RE: [TCML] Oscilloscope methods for showing Ringdown
If one is using a static gap, this will not work. With a static gap, the
timing is totally unrelated to the mains phase - it's purely chaotic. Only
if one is using a synchronous rotary gap will the gap firing be related to
the mains phase.
It properly answer the question, we'd need to understand exactly what the
goal is. If it's just a qualitative observation of the secondary ringdown -
like to determine 1st/2nd/3rd notch quenching, you shouldn't need anything
more than a standard triggered sweep scope, with any type of probe just hung
in the vicinity of the secondary. Just sync on the pickup probe and play
with the trigger level. Even with the chaotic firing of a static gap, the
scope will trigger at the same point of each bang.
Regards, Gary Lau
> -----Original Message-----
> From: tesla-bounces at pupman.com [mailto:tesla-bounces at pupman.com] On
> Behalf Of Skip Malley
> Sent: Wednesday, March 11, 2009 5:18 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Oscilloscope methods for showing Ringdown
> For scope triggering, try to sync the scope to the power line. Your
> spark will likely happen at the same phase point of the AC. You can
> vary the phase and trigger point along the AC waveform.
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