Re: Measuring self-capacitance directly (Re: flat secondary)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Paul Nicholson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>

Steve Greenfield wrote:
> So it is a rule of thumb

For solenoids, you can calculate the effective capacitance, from the
dimensions of your coil, using some semi-empirical formulae.

Referring to 
 http://www.abelian.demon.co.uk/tssp/formulae.html

Use the first formula to work out Fres, use the second formula to
work out the effective series inductance Les from the DC inductance.

Then Ces = 1/(4*pi*pi*Fres*Fres*Les)

The formulas should give you an answer to within 10% for coils with
h/d > 1.5 and coil former thickness less than 5% of the coil
diameter, which covers most coils except the small table-top
variety.  It'll probably get you closer than attempting to measure
Cdc and applying a 50% rule of thumb.  Maybe someone will be nice
and code the arithmetic into one of those web page calculator
things. 
--
Paul Nicholson
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