RE: Dimensions of my flat spiral coil

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

Original poster: "David Thomson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>

Hi Antonio,

>If you measured it by connecting a capacitance meter across the coils, what
you measured is a parasitic effect of the meter, that depends on how it is
built. The reading may be on the right magnitude order, but it is surely not
the "self-capacitance" of the coil.

Thank you, I've had my doubts about the accuracy of the capacitance
measurements.

Can you briefly explain the "parasitic effect of the meter?"

>You can have an estimate value of the self-capacitance of a coil by
measuring the capacitance between the coil and the ground. Connect one of
the terminals of the coil to one terminal of the capacitance meter, leaving
all other connections open, and connect the other terminal of the
capacitance meter to ground.  The "self-capacitance" of the coil is then
about one half of this value. This is correct for a solenoidal coil. For a
flat coil would be close too.

Thanks, this is really useful information.

Dave