Re: [TCML] Measured Q vs. Predicted

["Phillip Slawinski" <pslawinski@xxxxxxxxx>]

Okay, well the meter measures Q at 1000Hz.  I thought the frequency might
have something to do with the low value measured.

On Fri, Dec 26, 2008 at 18:18, Ed Phillips <evp@xxxxxxxxxxx> wrote:

> I recently acquired a nice LCR meter.  This meter happens to measure Q
> factor.  I was noticing that there is a huge discrepancy between the
> measured value and predicted value.  I was hoping you might be able to shed
> some light on this.  Lets take my secondary as an example.  This is for the
> bare secondary, no topload.
>
> Predicted:
> ---------------------------------------------------------------
> 39.7637 Ohms = DC Resistance
> 19.131 mH = Ldc-Low Frequency Inductance
> 246 = Q
>
> Actual
> ---------------------------------------------------------------
> 38.99 Ohms = DC Resistance
> 19.487 mH = Ldc-Low Frequency Inductance
> 2.785 = Q
>
> Now this secondary is probably not the best secondary in the world, but it
> certainly is not the worst.  Is there a reason why my measured Q is so much
> lower than that given by JAVATC?"
>
>    How does the meter measure Q?  At what frequency?   Seems to me the
> predictions and measurements agree remarkably well for the resistance and
> inductance since you don't necessarily know the dimensions of the coil
> accurately.  The Q is the ratio of the reactance of the inductor to the
> series resistance and hence is frequency dependent and unless you can
> control the frequency of the measurement the Q value is useless.
>
> Ed
>
>
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