Jim,
Thanks for response.
For unknown reason I am unable to respond directly to this group's postings the last few days. Sorry for my failed attempt ( rubbish in subject line ) couple a minutes ago. I try in this way again now.....
Basically you're right. However, my problem is that, even when I average the TI mode ( x 100 , x 1k , x 10 k etc ) the stability resolution ( though considerably improving compared to single shot )lags remarkably behind the Frequency and Period Modes ( which modes, as said, perform outstanding with better than e-11 ).
E.g. : while averaging a 100 Khz signal ( e-11 locked to frequency standard ) in the TI mode 10k ( = gate time = 4 sec ) the observed
5370A jitter is +/- 160 pS, which is not really too bad but for one reason or another this is far worse than a 1 Sec gated Period measurement ( differs > 4 magnitudes but, since the absolute 5370A jitter is > 20 pS, this magnitude comparison doesn't make sense ).BTW : Measuring 10 Mhz and above, the 5370A jitters only ( even in single shot mode ) only 20-40 pS which is perfectly within the specs.
So, I still wonder what makes the TI measurement mode differently from the Period measurent mode ? I was so naive to presume that both ( TI and PERIOD modes ) were counting during gate open time in the same way, only from/to different point on the waveform.
Is my guess correct that the ( 5370A ) TI and Periode counting systems are NOT based on the very same mechanism ?
Thanks for any further comments.
Peter van Daalen. PE1E ex PE1ECM