[time-nuts] Fast frequency counting question

Luis Cupido cupido at mail.ua.pt
Sun May 4 22:16:02 EDT 2008


Hi Bruce,

I don't know what you mean by low resolution
but I can easily think of more than 12 bit at
higher than 150Ms/s.

 > will tend to limit the effective resolution in determining the zero
 > crossing locations.

by no means zero crossing is to be used. we do have
much more information than that... phase info is all over
in all sampled points not just on zero crossings.
This is why I've said some transform to produce a spectrogram.

Maybe this is the reason why you mention the need of so many
integrations and the "unpractical" comment, as you are thinking
of using only a tiny fraction of the information available.

...

interesting topic :-)

Luis Cupido.


p.s.
however even tens of thousands of measurements
of 1ms windows is a few minutes !!!





Bruce Griffiths wrote:
> Probably impractical as the sampling noise is so high that it will 
> require  tens of thousands of measurements to get the noise down to the 
> required level and meanwhile the temperature etc will have changed 
> significantly. Also the relatively low ADC resolution and nonlinearities 
> will tend to limit the effective resolution in determining the zero 
> crossing locations.
> 
> Bruce
> 
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