[time-nuts] Newbie with questions

Brian Kirby kirbybq at bellsouth.net
Thu Jul 28 15:26:17 EDT 2005

I believe the SRS 620 is a better instrument than the HP 53131A.  The 
53131A has a single shoot resolution rated at 500 picoseconds.  From 
test I have run, it can vary 190 pS to +500 pS.

I am in the process of running variance test on my disciplined rubidium, 
and I baseline the counter and then compare against several references.  
The baseline consist of of connecting a 1 PPS reference to the time 
interval counter stop and start input, from the same timebase to the 
counter, and then using 1 PPS from 3 other references.  The measurements 
presented are 4 samples/sets averaged together (the actual samples of 
the datasets are much, much higher).

As a quick reference of my 53131A, the noise floor at 1 second is 
1.7x10-10, 3 seconds is 4.0x10-11, for 6 seconds is 1.4x10-11, 10 
seconds is 4.8x10-12, 30 seconds is 1.3x10-12, 60 seconds is 7.4x10-13.  
This test is still in progress, so I do not have data for higher 
averages (yet).

I believe this is something we should all do, to get to know our 
instruments.  Its a way to validate the data, considering that most of 
us do not have our test equipment in a calibration program.

Brian - N4FMN

lymex at vip.sina.com wrote:

>Q1E: which is better as for noise, Agilent 53131A or SR620?
>For Agilent 53131A, only the SDEV function is available. 
>I made the similar measurement as above (gate time=1s, N=100 
>samples). The SDEV is worse than those obtained by SR620. 

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