RE: Formula for Flat Spiral Coil

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Dave,
         If the dimensions in that formula are in inches (which the 
"8" and "11" suggest they are), the output will be in uH, *not* mH.

Regards,
malcolm

On 1 Mar 2002, at 16:34, Tesla list wrote:

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