On 04/02/14 11:10, Azelio Boriani wrote:
In the second sentence, I make the point that when you take two sample values,
at various taus, you really do not
average them but rather make their time stability contribution (trigger jitter
and resolution) less important relative to
the tau between them. This is by itself not an averaging effect.
Agreed that it is not an averaging effect, then taking two samples at
various tau is, for example, taking samples at 2 seconds instead of 1
second or using two samples for the actual tau under consideration?
Well, if you want to analyse the tau=2 s ADEV case, you need to use 3
samples, with 2 s between them, which is exactly what the standard
formulas use. If you have a systematic precision noise, that will fade
with 1/tau and overshadow any actual DUT noise.
If you have a 1 s tau sample series, you then only use every n sample
for your n*tau0 analysis. Remember that you should at least do
overlapping accumulation for better degrees of freedom and hence tighter
confidence interval.
The non-overlapping ADEV is only for historical reference.
Cheers,
Magnus
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