Re: acmi error found? - Test Equipment!?

["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>

Terry, 

Tesla list wrote: 
>
> Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net> 
>
> Hi All, 
>
> 4.      I disconnected the 0.1uF (I didn't have a 1.0uF handy) capacitor and
> 10K 
> resistor.  This raised the inductance reading to 221.977uH.  A shocking 
> 4.86% Jump!  I am measuring at 34kHz so I wonder if the effect would show 
> up at 60Hz?  However, this does add load to the secondary that really 
> should be wide open theoretically.

I stopped using the RC network a while back just to ensure a bare reading as
well. I haven't noticed any problems without it. 
>
> 7.      I removed the secondary and the reading was still(!!) 221.058!! 
> Thus, 
> the effects of changing inductance I saw seem to be totally related to the 
> test equipment I had connected to the secondary coil for the coupling 
> measurement.  The bare unconnected secondary coil itself has no effect on 
> primary inductance!!  I also note that the value of 221.058 is ONLY -0.20% 
> lower than acmi's predicted 221.510uH!

Wow! Another fantastic verification of your previous. I would not have expected
this. 
>
> So to make a long story short, it would appear that the error drift we see 
> between measurements and acmi's predictions may very well be due to the 
> test equipment placed into the coil's fields.  It appears the acmi may 
> indeed be predicting the coupling better than "I" can measure due to the 
> need to have test equipment "in there" while I take the real world readings. 
>
> At this point, acmi seems to be working flawlessly and beyond the level 
> where I can measure the error.  I think I have an absolute error of about 
> 0.3%, so acmi appears to be far better than is needed for any practical 
> coiling purpose.  I guess measuring primary to secondary coupling 
> coefficients with meters is an art that is no longer needed!!

I agree almost. Except for that last statement (I know, all in fun). Time to
get those smaller coil measurements, helix, cones, etc.. 
>
>   
> I should note that my secondary has always measured 75.4mH but programs 
> seem to like it to be ~1% higher.  I wonder if the high loss Sonotube is 
> responsible.  However, this number is insensitive and does not affect the 
> rest of the program significantly.

Yep, I was beginning to wonder about my sonotube coil as well, but then I
remembered your's was sonotube. Trying to find that 1mH difference would be
real brain teaser. 
>
> I would ask that these issues be included as a errata in the program's 
> documentation so 50 years from now someone will not take real measurements 
> again and go through all these problems all over again (like we do today
> :-)).

Yes, I hope this can get done. Of course, now I know how the UK coilers feel
when we write everything up in inches. 
>
> I guess it should be tested against conical primaries and solenoidal 
> primaries too to be sure that basically works but I don't have any 
> primaries like that.  Also, looking forward to hearing if the work other's 
> are doing confirms all this.

I sent a seperate post for my test today. I'll be digging into Marco's data
once more and another set of data. 
>
> Great work Paul!!  This shows what a fine computer modeling program can do! 
>  It looks like all one needs now to measure primary to secondary coupling 
> is your program!

Seconded!! 
>
>   
>
> Cheers, 
>
>         Terry