Rigol DHO914S Bode plot

[ebastler]

Has Rigol been providing timely fixes for bugs reported on their other DHO platform scopes?  I would have expected the second model series released to have less bugs and the DHO800 and 900 series to have even less.  If not less, then I would expect the bugs to be limited to UI layout and other series specific differences.

The DHO900-specific features (AWG, Bode plot, logic analyzer) are not available in the earlier DHO models, hence could not benefit from prior testing in the DHO1000 and 4000.

A few bugs were found in the basic scope functionality of the DHO800, mostly by Serg65536 (e.g. curves disappearing upon scrolling or zooming while in STOP mode). No idea whether these have crept in during the transition to a smaller FPGA, or have already been present in the larger DHO models -- I don't think the DHO1000 and 4000 have received the same attention and scrutiny here.

[Fungus]

Has Rigol been providing timely fixes for bugs reported on their other DHO platform scopes?  I would have expected the second model series released to have less bugs and the DHO800 and 900 series to have even less.  If not less, then I would expect the bugs to be limited to UI layout and other series specific differences.

The DHO900-specific features (AWG, Bode plot, logic analyzer) are not available in the earlier DHO models, hence could not benefit from prior testing in the DHO1000 and 4000.

And that's where most of the bugs are.

A few bugs were found in the basic scope functionality of the DHO800, mostly by Serg65536 (e.g. curves disappearing upon scrolling or zooming while in STOP mode). No idea whether these have crept in during the transition to a smaller FPGA, or have already been present in the larger DHO models -- I don't think the DHO1000 and 4000 have received the same attention and scrutiny here.

The only other one I know of is the serial decoder threshold voltage. The voltage level doesn't take into account the probe attenuation settings so it's only correct when probes are set to 1x. If you set the probes to (eg.) 10x then you have to set the threshold voltage voltage 10x higher for it to work.

Edit: One other bug I found - it doesn't save the setting for zoom/fine control when you push the horizontal timebase knob.

[iMo]

[ebastler]

That's TurboTom's video, and he reported this on the forum earlier:
https://www.eevblog.com/forum/testgear/rigol-dho804-test-and-compare-thread/msg5112108/#msg5112108

[Omega64]

Hi guys, can you confirm please that the Bode Plot function still doesn't work with the accuracy one would expect, neither with the latest firmware?

Cheers.

[TimFox]

I am still in communication with Rigol, but was unaware of any firmware updates since the first one in early October.

I noticed on another thread that there is an early November update that I haven't used--no one informed me, despite my having registered the product.
The release notes did not mention the Bode Plot function.

Over the next week, I intend to send them more data, after my original organized data report sent to them in late October, most of which I posted in this thread.

[Mechatrommer]

i tried on prototype board on DHO804 also get same wobbly effect...
https://www.eevblog.com/forum/testgear/rigol-dho804-bode-plot

[ebastler]

i tried on prototype board on DHO804 also get same wobbly effect...

First, congratulations on getting a signal from your replica AWG board! 

In your Bode plot, I can't see the characteristic periodic wiggles others have reported. The distortions seem more irregular, both on the phase and amplitude curve. Could you try to re-run the plot with more data points per decade? -- Also, what did you use for your device under test?

[Mechatrommer]

i tried on prototype board on DHO804 also get same wobbly effect...

In your Bode plot, I can't see the characteristic periodic wiggles others have reported. The distortions seem more irregular, both on the phase and amplitude curve. Could you try to re-run the plot with more data points per decade? -- Also, what did you use for your device under test?

if 50 points per decade, there are 5 decades there, ie 250 points, its going to be too long time to finish and a lot of front end relay clicking, the algorithm is too inefficient imho. maybe later if i need more serious DUT to specify, but i can already see the problem doing the short test, i suspect DHO800/900 use Vpp measured on screen to make bode plot, hence this will include noises and invalidate bode plot, so i guess no point to do more test with more data points.

i suggest using FFT method, i've done this long time ago with DS1052E and Hantek DDS3x25 iirc succesfully. i stated few suggestions to rigol on the linked thread (if they happen to get to the message). and the DUT i used in the test can be seen in the video linked in the thread linked above.

tbh, bode plot is not my cup of tea, i'm only exploring the full potential of the DHO800 fw and hw hack. attached is the bode plotter pc app i made like 10 years ago, and then never use it cheers.

[Lathe26]

I think I have a guess as to why the Bode Plot feature has weird bends or corners in it (the "wiggles" issue is separate).  They are simply drawing the points at the wrong horizontal position in the graph.  The measurements themselves are fine; it's just displayed wrong.

For some reason, at each decade boundary, the 1st sample to the right of the boundary has an unusually large horizontal jump that is inconsistent with the ones that follow it.  In contrast, the 1st sample to the left has a small jump that is consistent with the ones that precede it. 

In the 3 photos, 300 points per decade was used.  This made the delta Hz between samples small.  The 1st photo shows the cursor at 9.92 kHz, the 2nd at 10.00 kHz, and the 3rd at 10.08 kHz.  Notice the cursor make a small horizontal jump from 9.92 to 10.00 kHz while it is large for 10.0 to 10.08 kHz.  The 2nd jump should instead be slightly smaller than the first due to the logarithmic scale.

The Excel file and chart were taken directly from the Rigol's measurements generated by the same Bode plot.

I'll report this to Rigol's support.

Apologies if someone else already covered all this.