[time-nuts] What is the best counter for a Time Nuts?
Ulrich Bangert
df6jb at ulrich-bangert.de
Thu Oct 9 08:58:18 UTC 2008
Gentlemen,
first of all I would like to thank you for your feedback.
Reading in the literature that some of you supplied revealed that modern
counters may work even more tricky than i had though but that their
"tricky output" is NOT easily taken as the input for AD computations
without additional precautions.
> The Ref Output on the front panel of the SR620 is derived
> (1/10,000) from the
> EXT IN on the rear panel. So when you apply a 10 MHz signal
> to EXT IN you get
> a 1 kHz REF OUT. Appendix B in the PSR10 Rubidium source
> manual describes how
> to use this along with the arming function to average 1,000
> measurements per
> second resulting in 2E-12 per second on the display. i.e.
> very close to the
> HP53132A. So no external hardware is required and no PC to
> get this result.
After I had read this suggestion of Brooke I immediately gave it a test.
With a reference and a DUT both believed (due to other
experiements/measurements) to be stable < 3E-12 @ 1s I received the
results attached.
And of course you do not get a frequency value as
> second resulting in 2E-12 per second on the display
may indicate. The counter works in time interval mode in this
arrangement and you get 1 s data of delta ts between 0 and 100 ns that
need to be un-wrapped. I would judge that this method is well suited if
a DUT needs to be trimmed to 10 NHz with high resolution but I fear that
it does not help us in high stability measurements since the intrinsic
noise is still more than a decade too high.
Best regards
Ulrich Bangert
> -----Ursprungliche Nachricht-----
> Von: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Brooke Clarke
> Gesendet: Mittwoch, 8. Oktober 2008 23:43
> An: Discussion of precise time and frequency measurement
> Betreff: Re: [time-nuts] What is the best counter for a Time Nuts?
>
>
> Hi Bruce:
>
> The Ref Output on the front panel of the SR620 is derived
> (1/10,000) from the
> EXT IN on the rear panel. So when you apply a 10 MHz signal
> to EXT IN you get
> a 1 kHz REF OUT. Appendix B in the PSR10 Rubidium source
> manual describes how
> to use this along with the arming function to average 1,000
> measurements per
> second resulting in 2E-12 per second on the display. i.e.
> very close to the
> HP53132A. So no external hardware is required and no PC to
> get this result.
>
> Have Fun,
>
> Brooke Clarke
> http://www.prc68.com
> http://www.precisionclock.com
>
>
> Bruce Griffiths wrote:
> .....
> >
> > It is also possible to use a SR620 or a 5370 to take 1000
> > timestamps/sec. However may require using some external hardware
> > (frequency divider). For maximum accuracy and precision the
> resultant
> > data has to be logged and processed off line using a PC or other
> > computer.
> >
>
>
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