[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!  :)



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