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Re: Leader Strike Photo



Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 12:51 PM 9/26/2006, Tesla list wrote:
Original poster: Bert Hickman <bert.hickman@xxxxxxxxxx>

Hi Terry,

You and Peter are really breaking some new ground in TC research! However, the phenomena we're interested in span many orders of magnitude (in light intensity, current, and time), and optical measurements alone don't tell us the complete story. Also, there's no synchronization between the TC and the rotating mirror, leading to many more "misses" than successes.

And, although using LED's to show polarity is a great advance, it doesn't provide an accurate measure of current magnitude versus time. Although peak brightness does scale relatively linearly to LED current, no intensity measurement are presently being done (via a fiber optic coupling and PIN optical detector or phototransistor). The bar display approach was ingenious - too bad it is too slow. And, although using a series of LED's to fire at various current levels is another excellent idea, even this does not provide the accuracy that's available via Rogowski or Pearson type current transformer.


One could use a standard flash A/D with an LED on each bit. LEDs arranged in a row parallel to mirror spin axis. That will give you a binary encoded set of stripes, which could be processed by a program that looks at the image to give you current.




4. It may be impossible to capture actual streamer and leader growth without using considerably higher mirror speeds, much better synchronization, and (perhaps) an image intensifier. Maybe an inexpensive night vision scope could be interposed between the mirror and camera to obtain a poor man's version of an image intensifier to capture lower light events?

Higher mirror speeds usually use a polished metal multifacted prism driven by an air turbine (i.e. die grinder). The main limit is deformation of the mirror because of centrifugal force. Beryllium is what's used in the really high speed systems (light yet stiff), but steel seems to be quite popular, and wouldn't have the health hazards.