[time-nuts] Difference between HP 5370A and 5370B

Brooke Clarke brooke at pacific.net
Fri Apr 15 19:13:21 EDT 2005

Hi David:

There's an appendix in the Stanford Research manual for the PRS10 Rb 
oscillator that explains how to make 1,000 measurements each second and 
thus get 1 ps accuracy every second.  It involves using a precision 
external clock into the SR620 and connecting the Ref Out (1 kHz derived 
from the internal or Ref oscillator) into the External Gate input.  The 
Start and Stop signals need to be something like 10 MHz, or probably any 
frequency at or above 1 kHz.  And the gate is used to enable a 
measurement 1,000 times per second. 

Each second you could see a drift of 1E-12 and 1E-14 in 10 seconds!  I'm 
going to try using this method to set one Cs standard to the one I think 
is now set.

Note that some of the HP counters can display a large number of digits 
per second when measuring frequency, BUT NOT in time interval mode.

I like the SR620!

Have Fun,

Brooke Clarke, N6GCE

w/Java http://www.PRC68.com
w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml

David Kirkby wrote:


> That counter sure was a pretty high-spec device in its day. I looked 
> today in the Standford Research cataloge and they have the SR620
> http://www.thinksrs.com/products/SR620.htm
> but I note that has a 25ps single shot capture. I've not looked at the 
> current HP (sorry Agilent) specs on this sort of equipment. . . . .

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