Re: [TCML] Terry Filter Resistors

[Simon Dodd <simon@xxxxxxxxxxxxxxxx>]

Hey there guys, I have been following this thread since starting it  
and although my question was answered very early on I noticed that one  
of you offered plans off list for a home made wire wound resistor.  As  
I am very interested in building my coil as much as possible (rather  
than buying pre made parts) I was wondering if it would be possible to  
send me these plans.

Thanks again in advance,

Simon
--
Simon Dodd
Director/ Technical Manager
Yes Boss Music
UK
simon@xxxxxxxxxxxxxxxx
www.yesbossmusic.com

On 29 Jan 2009, at 15:20, Lau, Gary wrote:

> What are the dimensions of these resistors?  My 6"x28" secondary  
> coil's inductance is only 89mH, so 145mH seems huge.  Granted, the  
> resistor is wound with much finer wire with more turns, but it'll  
> make an interesting sanity check to see how many turns a secondary  
> wound to the same dimensions as your resistor would require to  
> achieve 145 mH.
>
> Regards, Gary Lau
> MA, USA
>
> > -----Original Message-----
> > From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> > Behalf Of bartb
> > Sent: Wednesday, January 28, 2009 9:17 PM
> > To: Tesla Coil Mailing List
> > Subject: Re: [TCML] Terry Filter Resistors
> >
> > Hey Gary, Matt,
> >
> > Confirmed today at 145mH on todays reading (leads). Also measured 992
> > ohms. Measurements with 27XT.
> >
> > I think Matt is correct and it's logical. If I do the math (noting  
> > that
> > the 27XT frequency is 1kHz):
> >
> > Z = 145mH x 6.28 x 1kHz = 910.6 ohms.
> >
> > XL = sqrt(992^2 - 910.6^2) = 394 ohms (note R-Z due to -sqrt).
> >
> > L = 396 / (6.28 x 1kHz) = 62.7mH
> >
> > Still significant, but then these are rather large wire wound  
> > resistors,
> > so not overly surprising.
> >
> > Regards,
> > Bart
> >
> >
> > Gary wrote:
> > > Please confirm "I just checked the resistor in question and it  
> > > measured 146mH at
> > 1kHz."  146 mH sounds about a million times too high for the  
> > inductance of a
> > wirewound resistor.
> >
> > > Matt wrote:
> > > I think part of the problem is that most LC meters don't measure  
> > > Inductance
> > directly. They actually measure the Z of the device and assume  
> > Z=XL, and
> > therefore L=Z/2pif, which for most inductors is close enough. For a  
> > wire-wound
> > resistor though, this is not a good approximation, since actually  
> > Z=sqrt(R2+XL2),
> > and R is no longer negligible. You could use the L?shown by the  
> > meter to calculate
> > what Z it actually read by Z=2pifL, then using the known  
> > resistance, calculate a
> > corrected XL? from XL=sqrt(Z2-R2)and from that, determine the  
> > corrected L by
> > L=XL/2pif.
> > > Matt D.
> >
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