Hi Andrew,It helps to understand the concept of how the frequency of the secondary increases the amplitude of the signal your looking for. This is due to equal and opposite reactance. The secondary has both L and C reactance. The self resonant frequency will occur when the inductive (Xl) and capacitive (Xc) reactances are equal. Reactance (X) is an opposition to current in an AC waveform. If we remove that reactance, we no longer have that opposition. Reactance is frequency dependent. Above or below the self resonant frequency, either Xl or Xc will be dominant, but "at" the self resonant frequency, Xl and Xc cancel out and we are left with a reactance of zero (no opposition). There are still impedances (resistive, dielectric, eddy, etc.), but no direct reactances. This causes a maximum current characteristic within the coil. It's this current increase that causes the voltage to increase on the scope when Xl = Xc, and that occurs when the frequency of the generator is adjusted to the self resonant frequency of the coil.
The fundamental frequency (f1) will not necessarily be the first rise in amplitude, but it will be the greatest rise in amplitude. The reason why is that there are harmonics above "and" below the fundamental. The fundamental frequency however will be very clear when you see it. The waveform on the scope will rise sharply and you will be forced to adjust the volts per division on your scope to view the waveform in it's entirety.
And yes, when you adjust the generator frequency, the width of the signal per time division will increase and decrease. However, when you hit and even get near the resonant frequency of the resonator, the amplitude will shoot up. How sharp (or narrow) that signal is will depend on the coil.
Use the 20V output on you generator (more signal for the coil). All scope probes are shielded. This shield is a braid at signal ground potential. The black clip should connect the scope and generator signal grounds together (not AC ground). Your diagram is correct. It's a matter of sweeping the generator to the correct frequency. Put the generator on a "pulse" output (square wave). Don't rely to heavily on the frequency meter (it can pick up fundamentals easily and give false readings). Simply use the generator and scope. Then increase the generator frequency into the kHz region and begin increasing the frequency slowly while watching the scope waveform. You can put the scope on Auto trigger for this. When you near and attain the resonant frequency, you will see the scopes waveform spike in amplitude. Attach a 20" length of wire to the probe end and just let it hang down and place the probe about 30" from the coil to start with. The reason I say "start with" is that the probe itself can influence the frequency a little. The further away you are, the less effect the probe has (probe loading). But for what your looking at, as long as you don't directly connect the probe to the coil, almost any distance within reason will work.
Take care, Bart Andrew Robinson wrote:
So I've asked for tuning help before and one or two people responded with a link which was somewhat helpful... but now I need to refine some questionsWhat im asking from the list now is two things, one question and a confirmation on setup...First, the general question which applies to all tuning setups. The link I was sent to learn to tune the coil can be found here: http://myweb.tiscali.co.uk/teslatutorial/MEASUREMENTSPR.htm In this explanation (and any other explanation out there) after you setup everything you are supposed to turn up the frequency on the signal generator until the amplitude on the scope reaches a max. At this max is your resonate frequency. Um........ I'm no electrical engineer but when you change the frequency shouldn't the sine wave get longer and shorter (Freq modulation) not get higher (amplitude modulation)????? What am I doing wrong because when I setup the test and do exactly what they say to do I dont get their results (amplitude modulation) I get frequency modulation as expected....... PLEASE HELP (BIGGEST PROBLEM)See these links to my server for diagrams of my setup. What I really need is an explanation of physical setup, not schematic.Secondary self resonance: http://host.atomiklan.com/tesla/scope1.PNGIn this first setup the signal generator has two ports. A 20v and 5v. Which should I use? Also each ports probe has red and black alligator clips. Red goes to base of secondary and black goes where? Is this diagram correct?Primary self resonance: http://host.atomiklan.com/tesla/scope2.PNGIn this diagram I just think everything is wrong. Can someone please correct my diagrams. Thanks_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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