RE: weird resonance with HV cap

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Leigh Copp" <Leigh.Copp@xxxxxxxxxxx>

Chris,

As you probably know, neither your function generator, nor your
capacitance meter are really producing enough current to simulate actual
operating conditions. The difference between the theoretical response
based on the cap meter reading and the measured fo may have more to do
with the cap meter reading. The fact that the cap meter typically looks
at a very limited range of frequency or dv/dt (depends on the kind of
meter) to make its measurement, may skew the reading significantly on a
capacitor with more dielectric. Your function generator probably has
much more output current than the cap meter, and is going to be able to
more completely polarize the dielectric in your homemade cap.

I'm a bit confused - you said you had the scope -and- the generator on
the secondary? Did you mean the gen was on the primary, and the scope on
the secondary?

Leigh


-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: March 16, 2006 6:42 AM
To: tesla@xxxxxxxxxx
Subject: weird resonance with HV cap

Original poster: Chris Estes <estescc@xxxxxxxxxxxx>

So I've got a function generator and a scope and I'm trying to build my
primary to match my secondary. The frequency I'm shooting for (as
measured with scope and gen on the secondary) is about 340 - 350 KHz.
So I've got my primary lying on the ground tapped about 2 turns in, and
when I use a small ceramic disk capacitor of value (measured with a
capacitance meter) 5 nanofarads I see the tank ringing at about 340 KHz
but when I substitute my homemade cap (also measured to be about 5
nanofarads) it rings at about 670 KHz. I measured both caps with the
same meter so I'm thinking this must be a secondary harmonic I'm seeing
but I don't see the tank ring at 340 KHz when I turn the gen down like
it should. Does anyone know whats up wit dat? Is there any reason why I
wouldn't see the fundamental and only the harmonics with a HV cap?