On 2/9/12 4:51 AM, WarrenS wrote:
Indeed, ADEV is for random freq variation not easily measured by other means. Temperature fluctuations do not cause random freq changes and the temperature's effect should be removed if one wants accurate long term ADEV numbers. Even daily diurnal cycles due to temperature can have major negative effect on ADEV numbers as low as 2000 to 3000 seconds, and if there is an Heater or AC cycling, then any ADEV numbers about a few hundred seconds can be due to TempCoeff, which should not be measured with ADEV or included in ADEV plots. This is much the same as a single outlier data point that can screw up the whole ADEV plot and make it pretty much meaningless and unrepeatable. Ditto for linear ageing, Should be remove first if one wants true ADEV plots.
Interesting point you make here. The rising ADEV at 100-1000 second-ish tau in a system that should be better is a classic sign (at least around here) that temperature effects are showing up.
However, how could one remove that effect from the raw data? And isn't the measurement of the "system", which includes the environmental effects.
I suppose you could run your widget in a temperature controlled chamber, get those numbers. Then run it in a less controlled benchtop environment, and get those numbers, and claim that the difference is environmental.
But at some point, what you're interested is the performance of the system in the environment in which it will be used. If you need good ADEV performance at the 1000 second tau, then you need an oven, a vacuum bottle, or a better design that's less environment sensitive.
(difference between TRL6 and lower, for those into such things) _______________________________________________ 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.
