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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: Re: Do you now deny you posted a sentence which tied together "model"..."fig B1"..."possibility of skin effect" ... posted by Tom Dawson on June 11, 2004 at 14:13:16:
The article that is found on capacitors.com has the figure links at the end..I referred to the model in fig B1, but it actually was called "fig b1, b2, table b1" in the link..I'm now using the article as it comes from Jungs website..and for accuracy, I should have referred to fig B2, which is the equivalent circuit (what I called "model"). As figure B1 is only a physical diagram of a cap.In any case, neither refer to a small value cap 35 Hz, although some of Jungs text does...
Tom: ""None of that is germane to the particular test relative to DA. If I were to doubt your integrity I would get the clear impression that you are attempting to obfuscate the issue after being called on your spurious derogation of the measurement under discussion.""
Who said it was relevant to DA? I asked five questions at the beginning of the thread. Let's recap them...
First Q...Did you do a test comparison between same capacitance polypro's with only the Ctest voltage rating changed? That would almost show the variation in errors caused by the electric gradients in the dielectric. I say almost, because to get the higher voltage, they have to change the dielectric thickness, then increase the effective plate area to compensate..How they get that additional plate area will affect both esl and esr, as well as possibly making the unit more prone to skin effect based capacitance drop, depending on construction technique used and lead exit strategy.(hee hee...had to get that phrase in there somehow..).
So, I'm looking for any evidence that skinning may have been involved..and changing the unit voltage (only one variable changing)certainly can be by geometric changes, or just by forming time..
Q2: Did you compare save voltage polypro's with different capacitances? That would look specifically for the geometry based skinning of the unit..As part of that, possibly just paralleling two polypro's of the same value as Cref, to double the test leg capacitance and compare to a larger Ctest.
Same exact subject, just looking for it by changing only one other variable..
Q3: did you try baselining the rig with a pair of identical polypro's for Cref and Ctest?
Answered a while ago.
Q4: How did you test the summing bridge to make sure that the error presented to it did not cause any input saturation based effects that generated a recovery period..From my earlier days of test using this type of equipment, I always had to watch out for the amp capability to recover from input "overload", usually a speed/amplitude phenomena. Sometimes, I had to put a front end resistor fed diode bridge, to very quickly limit the output drive being sent to the input stage..into a 50 ohm coax, that style of bridge gave me clean sub nanosecond truncation and recovery, alowing the settling time to be eliminated.
Answered a while ago.
Q5: Has anyone updated this test setup using this generation of IA's, to make the circuit useable for capacitance values in the range of wires?? I can see the Cref needed already..a pair of copper pipes, ten feet long, arranged coaxially, and spaced every 2 feet so often with a teflon ring.
Essentially, how do we apply the test to small capacitance wires??
I realize that publishing an article like this limits the authors, sometimes these types of issues get dropped to the cutting room floor. So I would guess that some of my questions have been addressed, some perhaps not...
But certainly worthy of an update, don't ya think?
Obviously, that was the menacing part of the post..the part that netted me the "jneutron your full of crap" response from John Curl..
Cheers, John
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Follow Ups
- Hmmm..I see why we did not see eye to eye.. - jneutron 06:50:36 06/14/04 (0)
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