On Sun, 01 Jan 2012 18:30:24 -0800, Hal Murray <hmur...@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! :) _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.