The trouble with ADEV is that if you average a long time it papers over anomalous events like crystal jumps. An alternative measure might be to, instead of averaging, simply keep track of the worse case change in frequency during 1 sample period. Sort of like peak jitter versus rms jitter.
Rick On 4/9/2014 3:38 PM, Hal Murray wrote:
I've been watching the discussions and graphs for a while. ADEV seems appropriate for cases where the noise pattern is "nice". How does ADEV work if the noise isn't nice? Are there alternatives? What's the mathematical term for the type of noise that works well with ADEV? I can think of 3 examples: Crystal jumps GPSDOs going into holdover. Power lines make all sorts of interesting not-quite jumps. Is there a way of characterizing that sort of event? How do I turn a pile of data into a useful graph or chart? What does an ADEV graph look like if the data has crystal jumps? I'd expect that something like crystal jumps would follow some sort of power law: the bigger jumps would be less frequent. But it wouldn't surprise me if the GPS or power lines had an underlying mechanism that turned into a different pattern.
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