Hi Volcker, Bob, I guess it depends on what one needs. The SR-620 is probably more of a gizmo to play with when one likes to manually adjust things or needs the better time interval resolution.
The HP unit is more of a fire-and-forget unit. Me having the benefit to be able to chose, I would generally prefer the HP unit. It's cheaper too! Also if HP says its a 12 digit per second unit, then it probably is doing that, albeit with some caveats as the manual states.. Bye, Said Sent From iPhone On Mar 17, 2013, at 17:23, Bob Camp <li...@rtty.us> wrote: > Hi > > This brings up the basic "how bad is it" question. Since the counter is > fundamentally a 200 ps gizmo, a simple period measurement at 1 second will > give you ~ 10 digits per second. That's with no magic multiple sample stuff > at all. At an offset / noise / what ever state where the multiple sample > stuff works 100%, you get ~ 12 digits per second. I doubt you ever get > everything so "perfect" that you are down to 10 digits / second. > > Bob > > > On Mar 17, 2013, at 7:41 PM, Said Jackson <saidj...@aol.com> wrote: > >> 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 <li...@rtty.us> 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, saidj...@aol.com 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, >>>> ail...@t-online.de 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 -- time-nuts@febo.com >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>> >>> _______________________________________________ >>> 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. >> _______________________________________________ >> 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. > > _______________________________________________ > 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. _______________________________________________ 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.
