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RE: acmi error found? - Measuring techniques?
Original poster: "Ross Overstreet by way of Terry Fritz <twftesla-at-uswest-dot-net>" <ross-o-at-mindspring-dot-com>
This brings up a question that I have had for some time now... How should we
be measuring primary and secondary resonant freqs? Should we measure the
freqs with the coil in "operating" configuration or should we separate the
primary and secondary. I'm guessing that we should separate when we are
comparing the resonant freq to values calculated using computer programs and
we should measure it in place when trying to verify that the secondary and
primary freqs are the same.
This is really important to me right now since I'm trying to get my big tube
Subject: acmi error found?
Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
I went back and measured the inductance of my primary with the secondary in
the various positions. It changes! (ok, I knew it would from past
experience ;-)) It appears as the secondary nears the primary coil, the
primary inductance drops by about 3.66%. I plugged the measured values
plus the measured value of my secondary (does not make much difference)
into my spread sheet at:
The drift is gone compared to:
Apparently there is something about the secondary that is decreasing the
primary inductance. I don't know what... Perhaps the rising capacitance
is cancelling a bit of the inductance??
The "Reading (Hz)" is the frequency of the primary resonated with a 100.3nF
cap. The repeatability is within 0.1% and the absolute accuracy should be
within 0.3%. Needless to say, I was really carful and used a bunch of
tricks to try and get this measurement to be accurate. It is not easy...
It looks like acmi has about -1.0% error assuming I messed up position 4
originally which this would indicate I most certainly did (starting to
trust the program more than me now ;-))