> Steve > > Just dont get too carried away. > Remember that the Hadamard deviation is only insensitive to linear > frequency drift. > If the drift is quadratic for example then it will affect the Hadamard > deviation. > > Bruce
Correct. This is another reason why the practice of removing systematic drift from raw data first and then computing ADEV on the residuals is quite useful. It allows you to separate the task of modeling systematic effects from the calculation of stability (ADEV) of the residuals. For example, you may suspect ahead of time, or you may find through analysis, that your DUT is following a slow logarithmic drift trend rather than just linear drift. Either way, you can remove the systematic effect to get to a closer measure of the intrinsic stability limits of the DUT. This is common with OCXO which have aged, say more than a few days, but less than a few months. It's pretty cool to see very linear drift rates each day, but to also notice that the rate itself slowly decreases week by week. As another example, you may find a strong correlation between temperature and frequency. You could plot ADEV of the raw data, and then plot ADEV of the temperature compensated residuals and observe the difference in the plots. /tvb _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
