Re: High Speed Streamer Pictures

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Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Gerry,

The actual strike will be the highest current on the graph.  Since 
strikes are only about 20nS long, the graph will just see a powerful 
blip at that instant since the bar graph's bandwidth is only about 1MHz.

You should be able to line up the graph with the photo pretty easily 
in most cases.  The green LEDs define the limits.  The 100kHz marker 
helps define time in the photos and helps a lot in detecting 
overlapped images.  The marker also dims with time indicating the 
direction of increasing time.

The LEDs are 0.1 amp each, so if say 5 of them light, the current is 
0.5 amps peak.

Cheers,

        Terry




At 11:22 PM 10/10/2006, you wrote:
> Hi Terry,
>
> This is cool.  In the picture, I see 4 streamers and 4 bar graphs so 
> I can associate a bar graph to each streamer.  Yes??  I presume that 
> the green LEDs being reference show the maximum scale for 
> interpretation of the red LEDs.  I'm still not clear what the 100KHz 
> marker LED is all about and how this differs with the current 
> measurement shown by the bar graph.  Is the bar graph not the 
> current in the streamer??  and is the measured current peak current 
> or something else??
>
> Gerry R.
>
> > Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
> >
> > Hi All,
> >
> > My new streak camera scope is working pretty good now!  So I picked 
> > a few real cool pictures to share.
> >
> > This is the setup:
> >
> > http://drsstc.com/~streakcam/pictures/31-0.JPG
> >
> > The LED bar graph goes from -2.5A to +2.5A in 0.25A 
> > increments.  Center is ground and there is a 100kHz maker on the 
> > far right.  It is directly measuring the current to the arc 
> > breakout rod.  There are green LEDs at each end for a reference. 
> > Time is from the bottom toward the top.
> >
> >
> > Here is a typical steamer buildup and strike:
> >
> > http://drsstc.com/~streakcam/pictures/31-1.JPG
> >
> > There is a 1/2 amp positive leader that goes about 1/4 the distance 
> > at 0.5A.  On the next positive 1/2 cycle the negative leader goes 
> > 1/2 the distance at 0.75 amps.  The next positive 1/2 cycle 1.75A 
> > leader just falls short of connecting (note the corona off the 
> > ground point).  The next negative leader connects and discharges 
> > the system (a super fast thing the scope cannot report accurately).
> >
> >
> > Here are two superimposed images showing both positive (bottom) and 
> > negative (top) strikes.
> >
> > http://drsstc.com/~streakcam/pictures/31-2.JPG
> >
> > I note that negative strikes seem to be brighter in general than 
> > positive ones.
> >
> >
> > Here is a set of three leaders just to the air that never connected:
> >
> > http://drsstc.com/~streakcam/pictures/31-3.JPG
> >
> > They seem to be about 0.5A to 0.75A peak.  The branching here seems 
> > like it draws more current than just a single leader.
> >
> >
> > Here is a negative leader (top) that connected but never "caught on 
> > fire" I guess.
> >
> > http://drsstc.com/~streakcam/pictures/31-4.JPG
> >
> > The next positive leader (probably) quickly strikes hard.
> >
> > Wild stuff!!!
> >
> > Cheers,
> >
> > Terry