Re: [TCML] Terry Filter Resistors

[FIFTYGUY@xxxxxxx]

In a message dated 1/28/09 2:52:44 P.M. Eastern Standard Time,  
mddeming@xxxxxxx writes:

>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(R^2+XL^2), 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(Z^2-R^2)and  from that, 
determine the corrected L by L=XL/2pif. 

    This would call into question even using such a  meter on a high-turns 
winding of any reasonable size, since it would  likely have significant DC 
resistance. I would think that a modern meter would  be smart enough to take a 
brief DC resistance reading for reference before it  went into "reactance mode". 
Microprocessors are cheap...
 
-Phil LaBudde

Center for the Advanced Study of Ballistic  Improbabilities
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