Re: Single Shot

From: 	Richard Wayne Wall[SMTP:rwall-at-ix-dot-netcom-dot-com]
Sent: 	Thursday, August 07, 1997 6:13 AM
To: 	Tesla List
Subject: 	RE: Single Shot

Malcolm responding to Julian wrote: 


>> I assume that the coupling between scope probe and TC is capacitive.
>It is.
>Many Regards,


Julian and Malcolm,

Capacitive coulping is good to pick up the E wave.  A small metal disc  
attached to the probe gives better and more directional results.  A 
sphere would work also, but would not be as directional.   

Magnetic coupling is also easy.  Fashion a small insulated wire coil 
and attach one side to the scope input and the other side to ground.  A 
couple of rigid turns of wire about 1" - 2" in diameter works great.  
It is also directional to a degree.

It's informative to monitor both E and B fields simultaneously, if you 
you have a dual scope.  I have, but have not integrated the two because 
my scope doesn't have that capability.  Also, dual measuring or mapping 
of the coil at different positions is very informative.  Best to do 
this at nonbreak out though.  Even driving the coil with a good signal 
generator is quite good.  The field gradients in a quarter wave 
resonator are fairly easy to map out.   

For those who do not have a scope or do not wish to chance damage to 
their scope, there are other effective ways to quantitatively "map" a 
Tesla coil.  The same magnetic pickup coil above can be attached to a 
radio frequency thermoammeter and the B field monitored.  Also, the E 
field may be monitored with a nonlinear pickup such as a common neon 
bulb.  Brightness of the neon bulb or monitoring with an analog meter 
works very well.

Be careful and make sure you are well insulated from the probes as you 
approach the resonator with the pick up probes.  On the scope probes, I 
have thought of protecting the scope with a bypass neon bulb(s) to 
ground to protect them in case there was an accidental arc over.  Sort 
of a small safety gap of sorts.  I haven't done this one yet.