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Re: This 90 deg phase shift business

Hi Richie,

At 09:24 PM 04/14/2000 +0100, you wrote:
>
>Hi Terry,
>
>I have been trying to resist the temptation to get involved with this
>transmission line argument,  because I don't have much experience in this
>field,  and the Tx-line maths is a little heavy for me too ;-)

Your missing out in all the fun of bantering back and fourth year after
year about secondary theory ;-))) 

>
>However,  your challange was too tempting for me to resist.  After all,  I
>have a scope, resonator, and a function generator at hand...
>
>> So give it a try and tell me what's wrong.  I think if I did all that
>RGLC
>> transmission line stuff I could explain the 5 degree phase shift (as I
>have
>> before) but there really isn't much that can go wrong with this test and
>I
>> invite anyone to give it a try...
>
>Well,  the funny thing is that I just did the test,  and I think I saw a
>90 degrees phase shift between the E-field at the base feed point and the
>E-field around the toroid.

Cool!  That's what makes this stuff so much fun.  Nothing ever works twice ;-))

>
>Now I know this is not what you and others have observed,  so I have
>likely made a gigantic blunder somewhere.  If so tell me where I went
>wrong ;-)

Gigantic blunders or what resonator theory is all about.  I got used to it
after MY first few dozen ;-))

>
>I took a resonator with toroid,  and base fed it straight from my function
>generator.  (Unfortunately this unit only has square wave output
>available,  my other unit is at work :(  I don't know if this affects
>anything ?

I'm switching mine to square wave and bolting on the toroid right now...

>
>I put a piece of wire in scope channel Y1 and wrapped this around the wire
>feeding the base of the secondary,  and got a volunteer to hold a scope
>probe from channel Y2 near the toroid.
>
>I then adjusted the frequency to get maximum level on Y2 (resonance !)
>The sinewave voltage surrounding the toroid seems to show a 90 degree lag
>when compared to the fundamental of the square wave driving the base of
>the resonator.

Yep I get the same waveform you do but when I switch to sine all is well.

>
>I don't know if using a squarewave to drive the resonator makes the test
>invalid.  I do know that the resonator still draws a sinusoidal current
>though.  In fact the heavy sinusoidal current draw caused the flat
>portions of the squarewave to sag under load !

Yep! dump the square wave generator and get a sine generator and all should
be well.  All the harmonics of the square wave may be hitting the harmonics
of the coil or something.  The current draw under resonance is really
messing with my generator. I may have used it too close to my TC or something.

>
>Take a look at these pictures:
>
>www.staff.ncl.ac.uk/90deg1.jpg
>www.staff.ncl.ac.uk/90deg2.jpg
>www.staff.ncl.ac.uk/90deg3.jpg
>
>I have always thought of the TC secondary as a series resonant lumped
>tuned circuit.  ie. Vsource, L, C, and R all in one big series loop.
>At resonance the current is in phase with the applied Vsource.
>Surely the individual voltage across L or across C must be out of phase
>by 90 degrees when compared with the applied voltage in order for the L
>and C to keep their properties.  CIVIL and all that ?
>Would you not expect a 90 degree shift for a lumped LC model ?

Of course, you hit on a very key point.  "Current" is maximum at resonance
and the current in the loop is all in phase at every point in the pure
lumped model.  The voltage across the inductor leads the current by 90
degrees and the voltage across the capacitor lags the current by 90
degrees.  Since the circuit is resonant and the losses are low, the
voltages across the inductor and cap are high.  So "I" really should be
seeing the expected 90 degree phase shift...

>
>I would be interested to hear your views.
>
>Sorry if I'm showing my ignorance,  as I've just joined this thread.

I will recheck my stuff and see if I can track down what is going on in
this experiment.

Richard Hull once warned my that trying to figure out resonator theory
would simply drive me nuts.  I think I am almost there!  I just need a
little work on this stuff a little more! ;-))

Cheers,

	Terry

>
>							Cheers,
>
>							-Richie Burnett,
>