[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: High speed Tesla spark photographs - StreakScope
Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
Hi,
I got the Streak Camera Oscilloscope all wired and put together and
got the first pictures in:
http://drsstc.com/~streakcam/instruments/BarScope-04.JPG
http://drsstc.com/~streakcam/instruments/BarScope-02.JPG
Here it is on top of the toroid ready to go. It is set to measure
the streamer current with a CT on the breakout point wire.:
http://drsstc.com/~streakcam/instruments/BarScope-05.JPG
Sorry, these are big like 1+Meg pictures but I did not want to loose detail.
First is the scope and all through the camera at 1/400s shutter
speed. Each LED is 1/2 amp and time is from bottom to top. The
calibration markers are 100kHz and positive is to the right: The
four sided mirror is at ~10,000 RPM.
http://drsstc.com/~streakcam/instruments/Scope-000.JPG
This picture was at 1/40s shutter and the grid lines over lap
badly. But the picture is cool in that you can see the ring up and
sort of a current decay after the main strike. There is a leader
above it that was caught too. If you look close you can easily see
the 200kHz 2nd harmonic that Peter has reported and its leader just
before the main strike.:
http://drsstc.com/~streakcam/instruments/Scope-001.JPG
Next I upped the shutter speed to 1/400 sec to get rid of the
overlap. This picture had one overlap but it is pretty clear
anyway. The streamer is negative and has a 2 Fo harmonic just before
the strike and then there is a positive current after the main strike
of 1 amp that lasts for about 7.5uS
http://drsstc.com/~streakcam/instruments/Scope-003.JPG
The last picture is just a leader with some odd details if you look close:
http://drsstc.com/~streakcam/instruments/Scope-004.JPG
I need to do that following:
1. Dim the grid LEDs so they are not so bright. They cause a little
ambient light wash now.
2. Wire the grid and calibration LEDs to only turn on only while the
current is > 0.5 amp (only during a current event). That will
eliminate the overlap problem and allow a far higher chance of
getting good shots with far slowwer shutter speeds (like 1/20s).
3. Make a little scaling control so that I can increase and decrease
the sensitivity. The scope goes to +-5 amps now but it should
probably be 2X to 4X that for leaders. Strikes are probably so
powerful and fast I will never really catch them properly.
4. "Fiddle" with things to get the pictures a bit better.
Cheers,
Terry