[Prev][Next][Index][Thread]
Re: Sparks to ground
Tesla List wrote:
>
> > > Subject: Sparks to ground
> > Subject: Re: Sparks to ground
> > > Subject: Sparks to ground
>
> >From hullr-at-whitlock-dot-comThu Nov 21 14:42:56 1996
> Date: Mon, 13 Mar 2000 22:28:59 -0800
> From: Richard Hull <hullr-at-whitlock-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Sparks to ground
>
<Bigggg SNIP>
> Bert,
>
> Much of what you have noted above, I agree with. However, as a video
> expert (my electronics engineering specialty), I understand fully what is
> taking place in the video imaging process.
>
> All the arcs recorded are dead horizontal, on screen. What little arc
> droop or radiusing that occurs, occurs totally within 20 scan lines.
> (vertically interlaced horizontal lines) The video frame is never
> continuously exposed for the 1/30 sec as in a common photo, even though
> the frame is, indeed, a 1/30 of a second exposure!! The horizontal lines
> (about 525 of 'em) are scanned in no more than 60usec per line . As the
> scan is interlaced, this entire group of 10 'key'lines in each field (two
> 1/60sec fields of alternating lines per frame) are scanned in about 625
> usec! As the rep rate (500BPS)is about one discharge per 2000usec, the
> normal exposure, of a standard video frame, will show only a single
> 'active' discharge channel of the resonator and never two. There is
> nothing to integrate!!! There are no successive arcs to pile up on the
> video camera's CCD sensor.
>
> It is even highly likely (3:1 odds in favor) that no actual active arc
> channel is recorded in any video frame!!!!! Thus, we are mostly seeing
> the result of heated air in the multi-thousand degree range with each
> successive video frame. This is a very close mime of the actual averaged
> arc channel current levels when the arc is on!
>
> It is also possible, with chance occuring sync locks, to record the
> coils violent white hot arc ativity without capturing a single 'active'
> arc channel over multiple 1/30 second exposures!! I know it sounds
> weird, but it happens. If you place a camera on high speed shutter,
> where the luminence integration winds up severely depressed, it is
> possible to film a running coil and never see an arc on the film (total
> darkness). The chances of such a perfect and continuous sync lock are
> rather slim. This is the reason that high shutter speed video shots of a
> coil are of almost zero value without full knowledge of the sync point.
>
> Regular old 30 hertz (~1/30 sec) frame rates are virtually ideal
> indicators of arc energy content.
>
> The light meter readings were taken with a Lumi-pro professional 'spot'
> meter in contact with the CRT face of a high qualtiy Panasonic BT-S901
> professional video monitor and not a standard old crummy TV set.
>
> Richard Hull, TCBOR
Richard,
Thanks for the additional info -- this provided me with much better
insight into exactly what you were describing! I was thinking about the
behavior of older vidicon tubes, which tend to exhibit significant lag
and saturation effects, often over multiple frames. A CCD sensor doesn't
suffer nearly as much from these artifacts. I now completely understand
what you are describing, and it definately makes sense!
Safe coilin' to you, Richard!
-- Bert --