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Re: Primary Qs
All,
I'd better add a note to the measurements (with the CP cap)
that I've just posted. I used the logarithmic decrement to calculate
Q but it is obviously wrong where a linear decrement is concerned
as Mark Barton has pointed out to me. My thoughts :
The thing we have to look for is a change in amplitude per cycle
to make any real meaning of this, in other words, the slope of the
decrementing waveform.
Thinkin' out loud: If you adjust the scope timebase so that the
cycles from different circuit configurations (different frequencies)
are plonked one on top of the other, we're looking for differences
in amplitude degradation in defining the Q's. I came up with a linear
equation that I'll throw open for comment :
Q = n*A0/(A0-An) where A0 is the amplitude of some cycle,
An is the amplitude of some succeeding cycle n
and n is the number of cycles over which A0-An is measured. Since Q
is defined as energy retained/energy lost per cycle, and energy is
proportional to V^2, this may need some modification, perhaps :
Q = n*A0^2/(A0^2 - An^2) ??
Thoughts on this one please. I need help (hopefully not
psychiatric :)
Malcolm