[time-nuts] evaluating an oscillator with the allan deviation

[folkert]

Hi,

Due to hobby-budget limits I build a very simple function generator
from an arduino and a dac ( https://vanheusden.com/Arduino/funcgen/ ).
I would like to evaluate its performance.

To do so, I setup another arduino which is connected to a pps signal
from a gps. This arduino then subtracts the timestamp from when the DUT
pulses (DUT = function generator) and when the GPS/PPS pulses (
https://vanheusden.com/Arduino/funcgen/osciltest.ino ). The result of
this is plotted using https://github.com/aewallin/allantools/ :
https://vanheusden.com/Arduino/funcgen/funcgen-allandev.svg

I'm far from an expert but this graph looks a bit too good to be true.
Can anyone spot the mistake I make in the process?


regards

Folkert van Heusden

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