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G0FTD > COILS 10.09.05 13:20l 43 Lines 1376 Bytes #999 (0) @ WW
BID : 000326243PZT
Read: GUEST DL1LCA OE7FMI
Subj: Pile wound coil problem.
Path: DB0FHN<DB0THA<DB0ERF<DB0FBB<DB0IUZ<DB0GOS<DB0EEO<DB0RES<ON0AR<7M3TJZ<
IK6PYS<N2BQF<ON4HU<GB7YFS<GB7PZT
Sent: 050901/1723Z @:GB7PZT.#24.GBR.EU [Kidderminster] #:32600 XSERV410d
Date: Thu, 01 Sep 2005 17:23:33 +0000
From: g0ftd@gb7pzt.#24.gbr.eu (Andy)
To: coils@ww
Subject: Pile wound coil problem.
Can anyone shed any light on the following problem ?
I have been constructing pile wound solenoids approx 8 x 3cm with 3 layers
in them but I'm not convinced that the measurement I'm getting is correct
on my equipment.
Depending upon the frequency that I measure the inductance at (10Khz - 400Khz)
I see an inductance value between 150uH - 250uH which has several peaks and
troughs when plotted against measurement frequency.
I'm confused !
How do I determine what the correct value is ?
Notes:
* I suspect that the relativly cheap bridge I'm using(£300 or US$600) is not
adequate at the low freqs (it does ok for higher stuff) OR quite simply
something that I'm missing in practice.
* I see that from my engineering reference books there appear to be 3 generic
pile wound formulae depending upon construction technique.
* The same books recommend a trial and see method rather than relying to much
upon strict formulae ;-)
Incidently the single layer coils I make work out to be accurate - e.g.
a 25uH single layer is correct but a 3 layer version measures on average
about 200uH.
Should I expect this magnitude of value or is my measurement technique invalid ?
Replies by bulletin *only* please.
Regards - Andy
G0FTD @ GB7CIP
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