Hi time-nuts, I'm doing oscillator-related research for my PhD and found this list recently. It's been a great resource in trying to refine my freq measurement setup and in starting to understand what's really going on inside my lab equipment.
I've been trawling the archives and have a question about measuring ADEV accurately with the Agilent 53131A frequency counter I have on hand. From the comments on this list and elsewhere, and the fact that TimeLab will talk to my 53131A directly, I have the impression one can use the 53131A for period measurements with which to calculate ADEV. But from GPIB command sniffing it looks like there's a lot of dead time between measurements: -- In period or freq mode* measurements take an extra ~130ms longer than gate time to return (but this seems to produce the correct measurements for TimeLab); -- in time interval mode they take about ~20ms; -- in totalize mode they take about 5ms, in keeping with "200 measurements per second" advertised in the brochure, but of course this is a simple counter and one loses the resolution of a reciprocal counter or anything smarter added in. Is it just generally assumed everyone is making period measurements on time scales long enough that any instrument dead time is ignorable? Or is TimeLab and everyone else silently applying the correction factor as described by the Barnes & Allan NIST paper (NIST technical note 1318)? Or is there a configuration mode I'm missing that prints measurements with more regularly? TimeLab's GPIB commands seem to be limited to "get current measurement" so I might not have the box set up right to start with. My research concerns oscillator drift on time scales of ~1ms to ~10s, so I'm guessing the 53131A with its 5-130ms of dead time isn't suitable for what I'm trying to measure. But I'd still like to know how folks are getting around this dead time issue with the 53131A for their measurements in hopes it'll shed light on how I can do the same without needing to pick up more gear and the inevitable shipping delay that will entail. I suspect someone will recommend that I get a time-stamping/continuous measurement box, which is probably the best solution. But I'm hoping there's a way around that in the short term so I can make these measurements sooner. 73, Dave * Others on this list have warned about using this mode because the machine does a lot of averaging but it seems like TimeLab needs the box to be in this mode regardless. I'm still looking for the part in the manual where HP/Agilent/Keysight owns up to this and describe how it changes the measurement. _______________________________________________ time-nuts mailing list -- firstname.lastname@example.org To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.