Hoi Bruce, On Tue, 16 Jun 2015 12:24:34 +1200 Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote:
> Using an ADC to sample a triggered damped sinewave easily achieves 5ps > resolution (eg Keysight Acquiris). With a better optimised waveform model > and least squares fitting routine greater resolution is feasible. > The accuracy is dependent on the ADC sampling clock stability. > An optical frequency standard derived clock may be required to maintain > ps accuracy for long time intervals. Do you mean the technique that Panek et al. [1] are using? IIRC he got that down to 0.5ps RMS now. And yes, the major source of error is the oscillator, according to [2]. Ripamonti et al. showed in [3] that using an LC tank instead of an SAW filter will result in something in the order of 2-10ps RMS (after temperature compensation). So this system is in the same region as an well designed time-to-amplitude converter based system. I really wonder which one would be easier to build. Attila Kinali [1] "Time interval measurement device based on surface acoustic wave filter excitation, providing 1ps precision and stability", by Panek andProchazka, 2007 http://dx.doi.org/10.1063/1.2779217 [2] "Random Errors in Time Interval Measurement Based on SAW Filter Excitation", by Panek, 2008 http://dx.doi.org/10.1109/TIM.2007.915465 [3] "High frequency, high time resolution time-to-digital converter employing passive resonating circuits", by Ripamonti, Abba, Geraci, 2010 http://dx.doi.org/10.1063/1.3432002 -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.