Re: Variation of secondary Q

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Terry,
           Any reason why you can't use the E-field to measure Q? 
After all, its differences/time you are after, not an absolute figure.

Regards,
malcolm
 

On 14 Mar 2002, at 20:03, Tesla list wrote:

> 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
> >--
> >
> 
> 
>