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Re: Windings vs. Diameter - errors
Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
At 07:05 PM 6/30/2006, you wrote:
To get my turns estimate, I usually place a piece of paper on the
coil and run a pencil over it. This gives a tracing of each turn
and makes it easy to place flat on a table in good light with a
ruler to count turns per inch, to whatever precision you want. eg
19G wire is .0335 in diameter by my micrometer. Over 2 inches on my
4 inch coil there are 58 turns ie .0345 inches /turn. Gives a wiring
percentage of 97% which is "better" than machine wound 19G of 95% by
your table.
Peter
http://tesladownunder.com/
Neat idea!! I have also put marked tape on coils and taken high res
digital photos. Blow them up on the computer in a graphics program
to mark off the turns... But easier still just to count them in the
first place ;-))
The new little coil measures 17.41mH.
It measures:
985 turns (exact)
2.992 inches in diameter of the form but not with the wire diameter
added (#30 at 0.0116 inches in diameter via a new Starrett 436 micrometer.)
11.50? long
That works out to.... r = 1.4989... 16.965mH by Medhurst.
So the wound coil is 2.6% over Medhurst predicted. That is vastly
better than I have ever guessed before ;-))
If we assume I made an error in the diameter, it would work out to
3.042 inches which is far inside what I can measure. So I might be
seeing the Medhurst formula's error now ;-))
MandK gives 17.06422mH which is only 2% low. But the "other" meter
(I don't normally trust it) "matches" that at 17.06mH... So probably
all down in the measurement noise errors now... I have "standard"
caps somewhere...
But I think "I know the details" for such things now ;-)) Coils that
have their turns "packed or not packed" is a big deal.
Cheers,
Terry