On 06/06/11 18:40, J. Forster wrote:
IMO, the lesson is that digital scopes do not always accurately depict what a circuit is doing. Even a $50 analog 'scope would never have this issue.
Out of idle curiosity, what sampling mode were you using? (ACQUIRE menu on my TDS2024B).
In SAMPLE mode, you're guaranteed to see this kind of aliasing. It's usually best to run digital scopes (especially the cheaper ones with limited acquisition RAM) in PEAK DETECT mode.
What this does is keep the acquisition front-end running at maximum speed and stores the minimum and maximum values recorded in each 'sample bin'. You still only have 2500 data points out of the (say) 2.5 million the scope might have analysed, but the min/max will at least tell you "there's a signal here" even if the scope doesn't have the memory / resolution to tell you what that signal *is*.
If you decide that the burst is interesting enough to look at (and you know what the repetition rate is), you zoom in (TIME/DIV and H POSITION controls) as normal.
I seem to recall someone covering this in a Youtube video. Probably Jeri Ellsworth (jeriellsworth on Youtube or Twitter) or Dave Jones (EEVBlog).
It's a big, nasty beartrap and one that's all too easy to fall into. -- Phil. li...@philpem.me.uk http://www.philpem.me.uk/ _______________________________________________ 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.
