[time-nuts] Rigol DS1102E down to $400
David
davidwhess at gmail.com
Mon Jan 2 04:11:19 UTC 2012
On Sun, 01 Jan 2012 18:30:24 -0800, Hal Murray
<hmurray at megapathdsl.net> wrote:
>A while ago, Rigol dropped the price of their 100 MHz 2 channel scope to be
>the same as their 50 MHz version. That was low enough for me. Since then,
>they dropped the 50 MHz version to $330.
> http://www.rigolna.com/products/digital-oscilloscopes/ds1000e/
Last year I considered buying a Rigol but ended up rebuilding an old
Tektronix 2230 instead. I judged Rigol's support lacking.
>Here is a picture of a PPS from a TBolt delayed by 1 second.
> http://www.megapathdsl.net/~hmurray/time-nuts/Rigol/scope-1sec.png
>The second/delayed pulse is about 10 uSec slow. If we assume the TBolt is
>much better than that, we can calculate that the clock on the scope is about
>10 PPM fast. (It limits the delay at 1 second so you can't delay a bit more
>and zoom in for a more accurate reading.)
Doesn't the Rigol have delayed sweep or is it zoom only? I know my
2230 can do this with a 50ns/div sweep speed although the internal
jitter might be too high. It is time to build a GPSDO to find out I
guess.
Bench oscilloscopes are not really intended for that kind of precision
in long duration jitter measurements. You could synchronize a divide
by 10 million counter to the 1 PPS and then use that to trigger the
oscilloscope to make jitter measurements of the GPS 1 PPS output. Some
oscilloscopes have provisions for an external reference clock in.
Hmm. That actually sounds kind of useful. Do any GPSDOs come with a
low jitter 1 PPS output?
Did you try triggering off of the GPS 1 PPS out and comparing it to
the phase of the 10 MHz signal directly? If it is reliably within
100ns then that should work to see the 1 PPS jitter.
>Here is another picture looking at the 10 MHz signal from a TBolt. (It's
>triggered on another PPS that is wide enough to see.)
> http://www.megapathdsl.net/~hmurray/time-nuts/Rigol/scope-2ms.png
>Note that the sweep speed is 2 ms/div, a wonderful example of aliasing. :)
>
>If I turn on the measuring stuff, it says 96.xx Hz which translates to 9.6
>PPM.
How can you possibly work with equipment that is almost 10ppm out of
calibration? Oh the humanity! :)
More information about the time-nuts
mailing list