Re: Inductance measurements of a flat spiral coil

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

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

> Keep in mind that if you combine a bunch of randomly selected resistors of
> the same value, the tolerance goes as 1/Sqrt(N).  So, 100 1% resistors in
> series will be a 0.1% resistor.  The key is that the errors have to be
> independent (i.e. if they're all from the same mfr lot, and uniformly 0.05%
> high, it doesn't work...)

	Right.  The ultimate value depends on the mean resistance, and in a lot
of 1% resistors it is very unlikely that it will be equal to the nominal
value.   A very long time ago an engineer with whom I worked decided
that he could hook 10% resistors (paralleled in this case) in lots and
get an improvement in accuracy more cheaply than by using precision
resistors.  Total bust.

Ed