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AC AMP METERS


Quoting Ed Sonderman:

 ES> Richard,

 ES> In the recent edition of TCBA News (volume 14, #2) on page 4 
 ES> it shows using an amp meter to tune a Tesla coil by placing  
 ES> it in series with the system RF ground at the bottom of the  
 ES> coil.  Has anyone tried this? What kind of current readings  
 ES> can you expect?  

I have seen rms current readings that pegged my 60 amp meter on
my large coil. At reduced power 30 - 40 amps was typical. This
improves with the ground path BTW.

 ES> Do I need a special high frequency meter for this?  

No.

 ES> Since I don't want to be trying to read the meter with my    
 ES> head right next to the coil, can you extend the ground       
 ES> wiring out a ways without affecting the tune?

Any extension of the ground path acts exactly the same to the
coil system as if you added wire to the secondary. But this wire
secondary wire "extension" has absolutely no function to the
coil. It is not coupled into the primary. It will mush the tune
up a bit. For experimental purposes it is OK. I use a standard
current transformer and run a remote lead to the ammeter some
distance away. The reading is accurate, and does not require
ground path modifications or close proximity to the coil.

 ES> The article mentions connecting the primary and secondary    
 ES> together at the ground point if the transformer does not     
 ES> have a center tapped ground.  We have discussed this before  
 ES> and you reccommended against it because of the lethal        
 ES> potential of 60 cycle current in the secondary. If I change  
 ES> from neon transformer power to a pole transformer how do I
 ES> modify my circuit since I don't think the pole transformer   
 ES> has a center tap on it's primary (our secondary)?

I am a little confused because of your wording, but the wiring is
easy. The only time you HAVE to ground one side of the primary is
if the step-up xfrmr has only one high-voltage bushing. Without a 
second HV terminal to work with, you have little choice but to
ring the tank circuit off of the RF ground.

The wiring differences on transformers without center taps really
only apply to the filtering and kickback protection circuits. The
tank circuit wiring is not changed.

Richard Quick


... If all else fails... Throw another megavolt across it!
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