RE: Formula for Flat Spiral Coil

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Dave,

The spiral formula is

L(uH)=(NR)^2/(8N+11W)

L is the inductance in "micro" heneries or 1/1,000,000 of a henrie.

The dimensions are all in inches.

Be sure you watch how the R and W are defined:

http://home.earthlink-dot-net/~electronxlc/formulas.html#spiral

Cheers,

	Terry


At 04:37 PM 3/1/2002 -0600, you wrote:
>I made an error in my post.  The formula I use is
>
>L(mH)=(NR)^2/8R+11W
>
>This is the formula I'm having trouble with.
>
>Dave
>
>-----Original Message-----
>From: Tesla list [mailto:tesla-at-pupman-dot-com]
>Sent: Friday, March 01, 2002 2:51 PM
>To: tesla-at-pupman-dot-com
>Subject: Formula for Flat Spiral Coil
>
>
>Original poster: "David Thomson by way of Terry Fritz <twftesla-at-qwest-dot-net>"
><dave-at-volantis-dot-org>
>
>What am I missing in this formula?
>
>L(mH)=(NR)^2/8N+11W
>
>N=number of turns
>R=average radius in inches
>W=width in inches
>
>Figuring for
>N=165.2
>R=7.063 in
>W=13.875 in
>
>L=16529.21cm or 16.529uH
>
>I would have expected the result to be in mH.
>
>In the past I just assumed I wasn't smart enough to do the calculation right
>and just divided the result by 1000 to get mH.  But now I'm using MathCAD
>and it is calculating exactly as I did.
>
>Should the formula for inductance of a flat spiral coil actually read...?
>
>L(mH)=(NR)^2/(8N+11W)/1000
>
>Dave
>
>
>