Re: Variation of secondary Q

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Paul,

I was testing this out, but I have run into a significant problem.  The
ring down current is tiny.  With 10V P-P in, I only get about a 200uA base
current signal:

http://hot-streamer-dot-com/temp/PaulsQexp-1.gif

Here is a simulation:

http://hot-streamer-dot-com/temp/PaulsQexp-2.gif

The scope only goes down to 1mA per division and the signal is flooded with
natural EMI being filtered out in the base current and riding on our signal
of interest.

So, the measured base current is too tiny to be useful :-(

Cheers,

	Terry

At 12:36 PM 3/13/2002 +0000, you wrote:
>It occured to me that if someone has one of those nice digital
>scopes that can be remote controlled over a serial RS232 connection,
>then they would be able to carry out an interesting experiment.
>
>A TC secondary is set up and driven by a low frequency, sharp
>edged square wave into the base, so that the coil rings down at
>its 1/4 wave Fres at each edge.
>
>The scope captures the base current waveform and downloads to the
>PC.   
>
>A PC program analyses the trace to determine both Q and Fres by
>matching the ringdown waveform to a function 
>
> A * cos(w*t+theta) * exp(-rt)
>
>and finding the parameters A, theta, w, and r which give the
>closest (least squares) match to the waveform.
>
>A 2048 point trace would give around 0.1% accuracy on the Fres
>measurement, and an 8 bit vertical resolution would give about 
>0.4% accuracy on Q.
>
>The program could be left running for a week or two, recording the
>values of Fres and Q into a data file which could then be compared
>with environmental factors.
>--
>Paul Nicholson
>--
>