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Rigol DS1000Z series buglist continued (latest: 00.04.04.04.03, 2019-05-30)

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frozenfrogz:
I could not reproduce it at that time, but maybe I did not try hard enough ;)
Would be interesting to see if it can be tracked down to certain behavior / sequence of operation.

Fungus:
This has had its own thread:

https://www.eevblog.com/forum/testgear/help-my-new-rigol-ds1054z-shows-a-weird-double-trace/msg1363145/#msg1363145

Porcine Porcupine:

--- Quote from: Fungus on March 04, 2018, 11:12:38 am ---This has had its own thread:

https://www.eevblog.com/forum/testgear/help-my-new-rigol-ds1054z-shows-a-weird-double-trace/msg1363145/#msg1363145

--- End quote ---

That's the thread I started about it several months ago. I wasn't sure what the problem was then, but now I'm convinced it's a bona fide firmware bug that deserves Rigol's attention.

Fungus:

--- Quote from: Porcine Porcupine on March 04, 2018, 11:36:42 am ---
--- Quote from: Fungus on March 04, 2018, 11:12:38 am ---This has had its own thread:

https://www.eevblog.com/forum/testgear/help-my-new-rigol-ds1054z-shows-a-weird-double-trace/msg1363145/#msg1363145

--- End quote ---

That's the thread I started about it several months ago. I wasn't sure what the problem was then, but now I'm convinced it's a bona fide firmware bug that deserves Rigol's attention.

--- End quote ---

I still think it's a hardware limitation in the circuit that copies raw sample data to the display.

It simply can't apply a wide-enough filter to display it correctly (which is understandable - it would need to filter an awful lot of data for each screen pixel). As such, it can't be fixed by firmware.

I'd be interested to how other oscilloscopes deal with this problem (in theory they should all do it to some extent!)

Porcine Porcupine:

--- Quote from: Fungus on March 04, 2018, 11:52:32 am ---I still think it's a hardware limitation in the circuit that copies raw sample data to the display.

It simply can't apply a wide-enough filter to display it correctly (which is understandable - it would need to filter an awful lot of data for each screen pixel). As such, it can't be fixed by firmware.

I'd be interested to how other oscilloscopes deal with this problem (in theory they should all do it to some extent!)

--- End quote ---

One thing that convinced me it's stuck in peak detect mode is that I was able to produce a trace with MATLAB that looks exactly as it should by simply downsampling the raw data to the same number of points displayed on the screen. I assume Rigol's normal acquisition mode is supposed to do the same thing in software to go from acquisition memory sample points to the points displayed on the screen.

Another thing that makes me feel it really is stuck in peak detect mode is the traces in both normal and peak detect modes look the same.

Here's a trace captured in normal mode:



And here's one captured in peak detect mode:



Both traces look like classic peak detection to me. If it was actually switching modes when the setting was changed, I would expect the traces to look different (as they probably do on a DS1054Z that isn't affected by this problem). These two example plots don't line up point-for-point because I had to do a new sweep after changing modes to get it to draw a new trace.

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