[time-nuts] Difference between HP 5370A and 5370B
Poul-Henning Kamp
phk at phk.freebsd.dk
Sat Apr 16 11:02:51 UTC 2005
In message <42604A91.60407 at pacific.net>, Brooke Clarke writes:
>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.
I do this all the time with my HP5370B.
Recently, after I wrote a GPIO driver for FreeBSD, I have managed
to get it to spit out "binary format" timestamps, so now I can make
it take 5000 measurements per second (with 20ps resolution and about
50ps noise) and get all the readings onto my computer, not just the
average/stddev.
I've been playing with doing FFT's of the samples and I belive I
could clearly see the modulation frequency on my old Rb unit,
but I never really found time to play a lot with it.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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