Bob, Thats why the 53132A counter reduces the resolution to one digit less at that frequency, and why we use an external divide by 2 for 10MHz measurements to regain that digit.
I wanted to be fair and compare apples to apples. If i use our 5Mhz input, the 53132A will be even better. We are always measuring at the "deadzone" because our gpsdo's are phase aligned via gps. But I can guarantee that the counter can differentiate xE-011 difference in frequencies, as we measure at this level all the time... And I assume the zero offset error of the Sr-620 is also due to this deadzone issue. Btw I was wrong the 53132A now sells for $999 on Ebay. The SR-620 is about $1450. Bye Said Sent From iPhone On Mar 17, 2013, at 16:22, Bob Camp <[email protected]> wrote: > Hi > > Be very careful of what the 53132(1) reports with the ref out connected to > the input. You are guaranteed to be in the "dead zone" on the counter when > you do that. > > Bob > > On Mar 17, 2013, at 5:33 PM, [email protected] wrote: > >> Hi Volker, >> >> there are some issues here, first the worst case frequency systematic >> uncertainty is 100ps for the 53132A, not 350ps as on the SRS unit or 500ps >> as >> you stated. So they are not the same, they are 3.5x different. >> >> From the Agilent manual: >> >> Systematic Uncertainty: >> Agilent 53131A Agilent 53132A >> tacc tacc >> typical 100 ps 10 ps >> worst case 300 ps 100 ps >> >> Notice the 10ps typical error, and 100ps worst case error. That compares >> to a 100ps typical error for the SR-620 or 10x worse typically than the >> 53132A. >> >> So we get 10x worse typically, and 3.5x less for the worst case - in my >> opinion these units are not even in the same class. >> >> Now for practical matters, I just measured the SR-620 we have with a >> randomly selected 53132A. Both connected to their own reference input. >> 2-second >> samples on both, and here are the results: >> >> The SR-620 shows a frequency error of -0.00203Hz consistently.That's >> 2.03E-010. Within its specifications but making the unit useless to me. >> >> The 53132A showed an error of only 2E-012 to 8E-012. So about 25x better >> accuracy! And the 53132A is showing 12 digits on the front panel as well for >> 2 second gate times at 10MHz. Nor does it require time-consuming and error >> prone and annoying internal adjustments to achieve this. >> >> What's even more damming for the SRS unit: as I increased the sample size >> (1s gate time is the max front panel selection, so I had to increase sample >> size instead of gate time) the error stayed persistent independent of >> sample size or thus measurement length. >> >> On the HP unit however, increasing the gate time made the error get smaller >> and smaller, and at 10+ seconds gate time I got 13 digits of resolution >> out of the unit, and an error of only 1E-012 at that point. >> >> So in summary, the SR-620 requires careful user adjustment of internal >> adjustment points. I don't have time to do that, so sent it in and paid the >> $600+ or so (if I remember correctly) for the standard calibration fee they >> charge. I got a unit back with the error unchanged, which was the original >> reason I sent it in to them in the first place. An error of 2E-010 makes the >> >> unit useless as we are in need of measuring xE-011 accurately. If I had >> time to learn how to calibrate the unit myself, I may do so, but even then >> you >> showed a 2E-011 error on your carefully adjusted unit, whereas I measured >> a 2 to 8E-012 error on a random non-adjusted 53132A unit here. Still about >> 3x to 10x difference in performance. >> >> If someone is interested in a swap of a working 53132A with input-c option >> for our SR-620 I would like to talk to you offline. I would even throw-in >> an FEI Rubidium reference in that swap, even though the SRS' sell for about >> $2300, and the 53132A'a go for about $1400. >> >> bye, >> Said >> >> >> In a message dated 3/17/2013 13:02:46 Pacific Daylight Time, >> [email protected] writes: >> >> >> I just powered on my SR and looked for the offset, when the 10 MHz >> reference is connected to the input (at a gate time of 1s without >> further averaging). It shows an offset of 0 to 400uHz which should >> represent a mean error of 2E-11, while the manual predicts an error of >> about 1E-10 (as Said told us, and as my manual tells me). That's within >> the spec. >> >> Unfortunately I don't have a 53132, but the manual of the HP predicts an >> error of E-10 - just the same value as with the SR. >> >> >> _______________________________________________ >> 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. > > _______________________________________________ > 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. _______________________________________________ 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.
