Re: acmi error found?

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Terry, 

Tesla list wrote: 
>
> Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net> 
>
> Hi All, 
>
> I went back and measured the inductance of my primary with the secondary in 
> the various positions.  It changes!  (ok, I knew it would from past 
> experience ;-))  It appears as the secondary nears the primary coil, the 
> primary inductance drops by about 3.66%.

Good find! I found something odd as well. I flipped the primary over (taps
unchanged) and measured a drop in coupling for the same s to p position. The
coupling dropped by 0.012! With the primary upside down, both windings are in
the same direction. But, with the "flip" I later realized there was also a drop
in primary height to the ground plane by ~7 inches. More testing to be done. I
made a pcv secondary base today that allows me to raise the secondary in 1 inch
steps, so I can now mimic your test bed. 

Glad you checked this. I expect there is something similar going on with my
coil, but I haven't put my finger on it yet. Although I didn't get an LCR for
Christmas, I did manage to win the football pool at work this weekend, so with
an extra $150 in my pocket, I may yet have that LCR meter. 

Take care, 
Bart 
>
>  I plugged the measured values 
> plus the measured value of my secondary (does not make much difference) 
> into my spread sheet at: 
>
>
> <http://hot-streamer-dot-com/TeslaCoils/Misc/TerryVSacmi2.gif>http://hot-strea
> mer-dot-com/TeslaCoils/Misc/TerryVSacmi2.gif 
>
> The drift is gone compared to: 
>
>
> <http://hot-streamer-dot-com/TeslaCoils/Misc/TerryVSacmi.gif>http://hot-stream
> er-dot-com/TeslaCoils/Misc/TerryVSacmi.gif 
>
> Apparently there is something about the secondary that is decreasing the 
> primary inductance.  I don't know what...  Perhaps the rising capacitance 
> is cancelling a bit of the inductance?? 
>
> The "Reading (Hz)" is the frequency of the primary resonated with a 100.3nF 
> cap.  The repeatability is within 0.1% and the absolute accuracy should be 
> within 0.3%.  Needless to say, I was really carful and used a bunch of 
> tricks to try and get this measurement to be accurate.  It is not easy... 
>
> It looks like acmi has about -1.0% error assuming I messed up position 4 
> originally which this would indicate I most certainly did (starting to 
> trust the program more than me now ;-)) 
>
> Cheers, 
>
>         Terry