[time-nuts] TimeLab and the Adev plot

[Magnus Danielson]

On 03/02/14 01:19, Azelio Boriani wrote:
> Magnus, please, can you elaborate this:
> > A common mistake is to assume you can average it out, but that gives you a different measure which does not
> > represent the ADEV values you are comparing with. The time between samples will scale down the relative impact of
> > the time-noise, but not really average it.
> That is, have I to increase the time between samples or take samples
> and average them? For example, go from samples every second to samples
> every 2 seconds or average two samples every second to obtain a sample
> every 2 seconds. The last method will (apparently) increase the
> resolution...

What I am saying in the first sentence is that taking the average of 
samples does not give you improved limit, but just add filtering which 
makes low-tau ADEV values which is biased to look better than the real 
ADEV for that measurement is.

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.

Cheers,
Magnus