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

David Kirkby david.kirkby at onetel.net
Fri Apr 15 19:59:08 EDT 2005

Brooke Clarke wrote:
> 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 think the 5370A or 5370B can, but without a manual, or an instrument 
to play with, I really can't say. But I have an instrument on order, and 
will search for a manual once I know the S/N, as I gather it is critical 
to get the right manual.

> I like the SR620!

There's one on eBay now


but the starting price is 5x more than I paid for the 5370B.

I like Stanford kit. Have several of their lock-in amps at work. I think 
we have more usable lockins than scopes!!

Dr. David Kirkby,

Please check out http://www.g8wrb.org/
of if you live in Essex http://www.southminster-branch-line.org.uk/

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