Re: Safety FAQ-discharge classification
Tesla List wrote:
> >From rwstephens-at-ptbo.igs-dot-netMon Aug 19 23:01:31 1996
> Date: Mon, 19 Aug 1996 18:19:20 -0500
> From: "Robert W. Stephens" <rwstephens-at-ptbo.igs-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: Re: Safety FAQ-discharge classification
> >>From hullr-at-whitlock-dot-comMon Aug 12 20:03:58 1996
> >Date: Mon, 12 Aug 1996 10:55:35 -0700
> >From: Richard Hull <hullr-at-whitlock-dot-com>
> >To: tesla-at-pupman-dot-com
> >Subject: Re: Safety FAQ-discharge classification
> ><boilerplate snippage>
> >Robert Stephens wrote:
> I have also seen a very rare (captured on video) Type 1, 'dart
> leader' come out off a pointed ground target about a foot long,
> coming out to meet a 10 foot long type 1, from my MTC system! The
> next video frame shows them meld into a solid strike path to the
> target. This is just like nature's lightning, eh?!
> A phenomenon which I have yet to hear anyone talk about, and which is
> especially evident in the streamer discharge to a grounded target in
> small tabletop systems is where a portion of the thin streamer seems
> to be twice as bright as the rest (majority) of the streamer. This
> effect is often near dead center in the length of the streamer, but
> sometimes is much closer to the target end. I've got video showing
> this effect near the target with my MTC unit with 10-12 foot scale
> arcs. My observations so far conclude that this brightened area is actually
> an overlap area where the streamer is split into two streamers,
> following a nearly identical path shape, but separate and parallel to
> each other over this brightening distance. Have you or anyone else seen this
> effect and figured out a reasonable explanation?
> Extremely grateful that someone upstairs clearly wants me to continue
> coiling, and pledging not to disappoint them,
Sorry about the car crash. Hope you are on the mend.
Oh yes, We have numerous video clips of this "hot knot" effect.
Because I am in the engineering end of video, this is easily explained.
Based on the normal video exposure rate 1/60 sec/field- 1/30 sec for
frame (two fields. You are seeing the banjo effect synced to 60hz--- the
normal exposure rate of the camera. As the scan moves to make an
exposure it is synced to something near line frequency in a camcorder.
(crystal generated) Horizontal sparks tend to occur 2-6 times (pops per
exposure), and the camera scans the same area, in sync, at a given point
along the arc channel three or more times. Arc channels move almost
imperceptively in calm air (air currents-convection). The parts that
tend to move the most pile up video luminance at that point in sync with
the 2-6 pops. Video is not High res and so at some points often as
many as 6 along the arc channel a super bright "sync" knot" appears.
A video artifact. We have yet to catch one on a high res B&W
closeup photo-- only the banjo strings show up as individual pops.
At a distance, and with fast, grainy film, even a photo can show this
knoting in really calm air. (camera fails to resolve the banjo strings)
Try this at a faster video exposure (1/250th or more) for more fun and
games. At really high rates and just the right sync with line and the
gap, the arcs can even disappear at 10,000 watts! This is most easy to
see with a syncronous rotary.
At the normal exposure levels, it is quite amazing to see these "knots"
of hot white light move along the arc channel as the non-synced camcorder
beats against the line frequency and gap rate which syncs the arc
Richard Hull, TCBOR