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Re: [TCML] Measured Q vs. Predicted



> 38.99 Ohms = DC Resistance
> 19.487 mH = Ldc-Low Frequency Inductance
> 2.785 = Q

> Is there a reason why my measured Q is so much
> lower than that given by JAVATC?

Depends what frequency the instrument is working at. At low
frequencies, Q is proportional to frequency.

  Q = 2 * pi * frequency * inductance / resistance;

For example, if your meter works at 900Hz, you'll get a reading
of around Q = 2.78.

Whereas, if the measurement takes place at a much higher
frequency, say, the resonant frequency of the coil, you'll
get Q = couple of hundred or so.

Above a few kHz, the resistance increases due to skin effect
so the proportionality tails off.

If you have a scope to hand, see if you can see what frequency
the LCRQ meter is working at.  Compare that with the predicted
resonant frequency of the coil.  That should resolve the
discrepancy.
--
Paul Nicholson
--
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