On Sat, 22 May 2010 15:08:50 +0100, Steve Hunt wrote:
>Given the importance of having resistive (lossy) chokes, I wonder how
>you determine the phase angle using your test set-up?
I showed that in my tutorial. I plot the curve of Z vs frequency, then do
curve fitting for the parallel resonant circuit to get values of R, L,
and C. Not as elegant as a VNA, but it works. :) This works for #43
(NiZn) without modification, but for #31 (MnZn), which can have two very
broad resonant peaks with a lot of turns, one must attempt to fit two
curves, one on the low end and one on the high end. The result is a very
rough approximation. See the early section of the tutorial where I showed
that the equivalent circuit is two parallel resonant circuits in series,
showed that some materials have both, some have only one, and then
compared #43 with #31.
As a very rough approximation, we can assume that the choke is
predominantly resistive if the Z is within about 30% of its peak value.
73,
Jim K9YC
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