From: mystuffs@orwell.net (Metlicka Marc)
Date: Sat, 03 Mar 2001 09:55:26 -0500
Subject: Re: [TSSP] Reactive part of base input impedance
terry, all i also noticed that at the point of highest topv the base v is at it's highest point. and i'm not sure it matters but i noticed that at the absolute mid point of were the highest v waveform, before it starts to fall off on either a slightly higher or lower frequency input, the base v waveform is in it's truest sine shape. on my scope this base v wave has a little bump in the peak, to either side of the frequency this wave shape would lean towards a leading or lagging type peak, saying that it would raise predominately to the left or right of the peak? i have video of this effect and it is how i found the very peak or accurate f1 point. on the point of highest top v and base v i was pondering whether the voltage was actually going resonant in my meter, but now i know it's also seen by others. great work and great new toy. marc "Terrell W. Fritz" wrote: > > Hi All, > > I got a new scope! A Tek 3012. The old one is sold so don't bother trying > to buy it off me... My TC budget will be a little busted this year :-))) > I have been thinking about the "big upgrade" for a long time and... ;-) > http://hot-streamer.com/temp/P3010015.JPG > > While playing with my latest toy, a thought occurred to me considering the > last post here. > > Since the voltage and current maximums into a resonator occur at slightly > different frequencies, the maximum power point will be somewhere in > between. The trace is my small coil scanned from 305 to 315kHz with a > P5100 top probe. > http://hot-streamer.com/temp/VmImPm.gif > > The yellow is top voltage, the blue is current in, and the read is the > voltage multiplied by current. > > So perhaps the "true" F1 is better defined as the point were Vin x Iin > reaches a maximum or the input Z is least? > > I just realized I shouldn't have been looking at top voltage in the scope > picture... but rather input voltage... Since the two frequencies, in any > case, are very close, this is more of a theoretical concern. I wonder if > the "true" f1 is (Fv + Fi)/2 or SQRT(Fv^2 + Fi^2)?? > > But perhaps the top voltage maxima and the input power maxima are exactly > the same frequency... Thus, the "true F1 is not so ambiguous... > > Much to ponder... > > Cheers, > > Terry > > --------------------------------- > Hi Paul, > > Neat! Great to know the measurements worked out so well! I am getting > used to doing this, so this was a very straight forward process this time. > > I looked at the probed coil for the resonant frequencies you mentioned and got: > > IbaseMax = 311.85kHz > VtopMax = 313.02kHz > > I plugged the 5100 probe into the HP meter so the frequencies can be > determined very accurately. However, the HP meter has a bit of an odd > input impedance so the probe/measurement "could" be off a bit. However, I > think it is pretty close. The signal generator has a resolution of 0.01Hz > and the HP meter reads out to 1uVacrms so the accuracy is super high if it > works... > > The scope is reading about 4.5% high on it's little readout and channel two > has a high offset. May be time for a calibration... > > Cheers, > > Terry
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.