G0FTD > COILS 02.09.05 19:49l 40 Lines 1284 Bytes #999 (0) @ WW
BID : 60425_GB7CIP
Read: GUEST DL1LCA OE7FMI
Subj: Pile wound coil problem.
Path: DB0FHN<DB0MRW<DB0SON<DB0SIF<DB0EA<DB0RES<DK0WUE<I0TVL<GB7YKS<GB7PZT<
GB7YFS<GB7CIP
Sent: 050902/1715Z @:GB7CIP.#32.GBR.EU #:60425 [Caterham] $:60425_GB7CIP
From: G0FTD@GB7CIP.#32.GBR.EU
To : COILS@WW
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
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