[time-nuts] HP53132A vs SR625

Bob Camp lists at rtty.us
Sun Mar 17 20:23:13 EDT 2013


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. 


On Mar 17, 2013, at 7:41 PM, Said Jackson <saidjack at 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 <lists at 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, SAIDJACK at 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,  
>>> ailer2 at 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 at 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 at 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 at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

More information about the time-nuts mailing list