[time-nuts] Looking for Wavecrest Visi
SAIDJACK at aol.com
SAIDJACK at aol.com
Sat Apr 7 19:48:21 UTC 2007
In a message dated 4/7/2007 04:08:20 Pacific Daylight Time,
cfmd at bredband.net writes:
The Wavecrests are wonderful tools, but they address a different problem
than
what normal time-nuts usually care about, so they are not a given perfect
counter for long term comparision. It is aimed at jitter.
Hi Magnus,
that's true for the SIA/SRT series of Wavecrest instruments.
But the DTS series (DTS-2070, 2075 etc) have features that your SRT does not
have, for example cable-length measurement with picosecond resolution.
The DTS units also have sophisticated external Arming features the SRT
doesen't have (two ARM inputs).
They also have A to B time intervall measurements so one can do a DUT to
Cs/Rb comparison for example with +-25ps accuracy per measurement, at 40000
measurements per second. Visi allows long-term high-resolution drift plots that
can be turned into ADEV plots.
Theoretically, this means +-25E-012 / rt(40000) = +-1.25E-013 measurement
accuracy per second if it's internal accuracy-noise is gaussian (I am not sure
it is) so it would average out when comparing one 10MHz against another
10MHz source.
I don't have the Visi software so I cannot use the HiPer 40Ks/s option so
the above remains theory until I can find the software.
Also, I don't think the SRT3000 can do two-input A to B measurements if I
remember correctly.
As of today, there is a DTS-2070 on Ebay (search for "Wavecrest Digital Time
System") for $900 buy-it-now from a known-good vendor.
In summary, I think the SRT is perfect for many-input parallel jitter
analysis, while the DTS is more of a traditional time-intervall-analyzer suitable
for time-nuts usage. BTW: I think they both are not very good as true
frequency counters.
bye,
Said
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