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.

[Mechatrommer]

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.

how can you say measurements are fine when you get wiggles as well in excel plot?

[Martin72]

I'll report this to Rigol's support.

On the Rigol EU and the Rigol NA page the last firmware update is from december 2023.
It doesn't look like anyone at rigol was interested in that.

[TimFox]

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.

how can you say measurements are fine when you get wiggles as well in excel plot?

The graphs I showed at the beginning of this thread were all done by taking the .CSV file of raw data ("Result") and graphing them through a separate graphing program (Grapher^TM from Golden Software), not using the Rigol display graph.  Besides the "wiggles", I found quantitative errors on the frequency of the -3dB points.

see  https://www.eevblog.com/forum/testgear/rigol-dho914s-bode-plot/msg5109597/#msg5109597

[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.

how can you say measurements are fine when you get wiggles as well in excel plot?

I expect some imprecision in the measurements for this device so the wiggles are expected.  However, the accuracy of the Excel graphs are night and day better because the macro-level graph mangling the scope displays with all the weird bends / corners are absent in the Excel graph.

[Lathe26]

I'll report this to Rigol's support.

On the Rigol EU and the Rigol NA page the last firmware update is from december 2023.
It doesn't look like anyone at rigol was interested in that.

I reported several bugs back in February and March that were well received by Rigol.  I've been told that one of them has been fixed for an upcoming firmware release (no release date).  This is more communication than I expected.

However... it's been 7 months since a firmware release.  I worry that Rigol is already abandoning their newest scope.

[Martin72]

That's the drama of the actually not bad Scope series, it's so quiet from Rigol's side.
They had updated the firmware so that it no longer crashed and that was it.
At least something is still happening with the 1000/4000s.

[Fungus]

That's the drama of the actually not bad Scope series, it's so quiet from Rigol's side.

Yep. It's getting a bit long now...

The list of bugs isn't long or complex, just silly errors like not multiplying the serial decoder threshold by the probe scale factor - one line of code to fix!

A couple of days work could probably fix most of them.

It's hard to understand what they're playing at after all the effort that must have gone into bringing this to market with a totally new OS, etc. Is the software team immediately disbanded on launch day...? 

[TimFox]

In October of 2023, I sent a long carefully-written memo, with graphs and attached .xlsx files, to the home engineering department (contact from US office), who acknowledged receipt.
The Bode function results were all for 1 to 100 kHz, log scan, with a simple well-shielded R-C filter (9 kHz nominal -3 dB point).
No answer since then.
When was the last firmware update posted for the DHO914S?
Anyway, when (very slowly) manually stepping through a narrow frequency range, the curves were monotonic (with a very small ripple), but the actual frequencies for -3 dB and -45^o were off by about 10%.

[Martin72]

@Fungus:
The problem with the bodeplot also needs to be fixed, as well as the incorrect (at least one) window coefficients in the FFT. A constant RBW unit designation would also be nice in this context, as well as possibly a display of the current memory points.
More complex features such as a peak or average function for the FFT will probably not come, as these two functions are not even available on the DS70000.
In my MSO5000 days, I had almost weekly contact with rigol support, with a lively exchange about bugs and feature suggestions, including the Bodeplot, which later became available.
Later, however, there were also answers like “we have to launch the MSO8000 first, then we'll probably continue”.
That was between 2018 and 2020, when I had my DHO800 and wrote to support twice, I never received a reply.
In the meantime, I think the chances of rigol taking “proper” care of the DHO800/900 series again are 30:70.
I rather fear that improvements will only come with a new series.
That would be very unwise of them, because it would destroy trust.

[Njk]

Did you ever tried to ask a big vendor, say TI, to improve a thing which is already sold? Not to fix the silicon, but to update the errata sheet or something like that. Rigol also went public. Perhaps the top guys there were indoctrinated in the same MBA school.

[2N3055]

Did you ever tried to ask a big vendor, say TI, to improve a thing which is already sold? Not to fix the silicon, but to update the errata sheet or something like that. Rigol also went public. Perhaps the top guys there were indoctrinated in the same MBA school.

Instrument vendors do actually fix things after release. Not maybe taking every customer wish, but if they find that instrument is not performing properly they fix it. Keysight does it. R&S does it (they sometimes take time but they fix). Siglent fixes things too, actually better than them sometimes.

Rigol is actually worst by a mile in that regard. I think that Fungus might not ne far with question if development is disbanded quickly after release. It certainly seems so...

[voltsandjolts]

The list of bugs isn't long or complex, just silly errors like not multiplying the serial decoder threshold by the probe scale factor - one line of code to fix!

There is a recent DHO1000/4000 firmware update which has apparently fixed the serial decode probe scale. It wasn't an exciting update but maybe something is on the way for DHO800/900.

https://www.eevblog.com/forum/testgear/rigol-hdo1000-and-hdo4000-12bit-oscilloscopes-launched-in-china/msg5547705/#msg5547705

[2N3055]

The list of bugs isn't long or complex, just silly errors like not multiplying the serial decoder threshold by the probe scale factor - one line of code to fix!

There is a recent DHO1000/4000 firmware update which has apparently fixed the serial decode probe scale. It wasn't an exciting update but maybe something is on the way for DHO800/900.

https://www.eevblog.com/forum/testgear/rigol-hdo1000-and-hdo4000-12bit-oscilloscopes-launched-in-china/msg5547705/#msg5547705

Problem is that it has been 2 years since 1000/4000 were released, in 2022....
Not what I would call maximum effort......

[Njk]

Instrument vendors do actually fix things after release. Not maybe taking every customer wish, but if they find that instrument is not performing properly they fix it. Keysight does it. R&S does it (they sometimes take time but they fix). Siglent fixes things too, actually better than them sometimes.

The monetary relationships between KS, R&S and their customers are of a very different scale. Similar to the service life of the equipment. The fact that Rigol, Siglent, etc. are also providing the fixes is actually a matter of good will. Perhaps it's more profitable to keep releasing new cheap toys frequently making many users happy to play with them. But I think it'll be not fair to assume that the vendors are intentionally evil. Although they may have a more important, actually not commercial customer, the capabilities can also be a factor. The software consumes the majority of man-hours, not the hardware. If you check the Rigol internet site, you can read that in 2024 a new SW development center is set up somewhere in center China, at the former silk road. That probably means that currently the SW development capability of Rigol is not great, while it's now too expensive to continue to order the development from outside than do that work in-house. Let's wait...

[Fungus]

There is a recent DHO1000/4000 firmware update which has apparently fixed the serial decode probe scale. It wasn't an exciting update but maybe something is on the way for DHO800/900.

They definitely know about the bugs.