Rigol DHO800/900 Oscilloscope Bug Reports + Firmware

[norbert.kiszka]

good (1-Ch.) peak rise time (1.35 ns)

1.25 Gs/s means one sample per 0.8 ns. 1.6 ns gives us two samples. Adding interpolation into account, this can be +- 50% of that. Maybe average acquisition method will be more precise to see more real rise time.

low noise floor

Yeah... on unconnected probes. Mine DHO924S (real DHO924S, not hacked one) is very sensitive to common mode from pulse power supply - in my case 15 mVpp. Im thinking about making linear power supply, to get rid of that spikes. Maybe also better probes...

[Robaroni]

I didn't think the probes were that bad, not Tek but easily just as good as my RTB2004 which didn't hold up - these might, they look stronger to me.

[dave991]

Just received the DHO924S.  Had a vintage Kenwood amp going through restoration. Thought I would do the calibration with the new scope and it’s AFG. Amp requires a 1Khz@1V signal to set the power meters. Set the scope up, connected to the input, and power meters were way to low and could not be adjusted high enough. Hooked the AFG output to my Leader voltmeter and the output is only .343V and not at all stable. I was able to get the scope to output 1V by upping the volts to 2.85. Not quite what I had in mind when I ordered this scope. I sent this to Rigol tech support and waiting for a response. This scope has too many issues to come with a “Calibration” certificate. If no response I’ll have to figure out the RMA process. It’s such a simple, basic setting that doesn’t work. My iPhone with a function generator app puts out a constant 1Khz@1V signal, but it costs $300 more than the scope.

[RFDx]

Just received the DHO924S.  Had a vintage Kenwood amp going through restoration. Thought I would do the calibration with the new scope and it’s AFG. Amp requires a 1Khz@1V signal to set the power meters. Set the scope up, connected to the input, and power meters were way to low and could not be adjusted high enough. Hooked the AFG output to my Leader voltmeter and the output is only .343V and not at all stable. I was able to get the scope to output 1V by upping the volts to 2.85. Not quite what I had in mind when I ordered this scope.

Looks reasonable. The AWG outputs an amplitude (Rigol means peak-to-peak) of 1V, that is 0.35V RMS. If you need 1Vrms then you have to increase the amplitude to 2.83V, which is exactly what you did. The output should be stable though.

[csuhi17]

Not quite what I had in mind when I ordered this scope.

My iPhone with a function generator app puts out a constant 1Khz@1V signal, but it costs $300 more than the scope.

Also 924S.
It seems good to me.

[Fungus]

Amp requires a 1Khz@1V signal to set the power meters.

RMS or peak to peak?

[Robaroni]

He's looking at RMS.
I didn't see any problems with the AWG, I did some Bode plots and FFT's and it was fine. Check the connector.

[Fungus]

Somewhere in the amplifier manual it should specify if it requires RMS or peak to peak.

[Mechatrommer]

Also 924S.
It seems good to me.

can you do me a favor to show low level performance of the AFG, specifically at 100kHz 20mV (pp) at 10mV/div scope setting?

[Robaroni]

Right in the AWG if you pick an amplitude the screen pops up and you can choose Vpp, RMS, etc. so even if the amp doesn't specify it you'll see it right away.

Newbie problem, I'm sure we all made it at some point, that's how we learn.

[csuhi17]

can you do me a favor to show low level performance of the AFG, specifically at 100kHz 20mV (pp) at 10mV/div scope setting?

after a few minutes of heating.
With and without a 20Mhz limit.

after warming up, the measured voltage decreased by 0.5 mV.
That is, the average: 22.543mV
Dev: 320uV

[ebastler]

Newbie problem, I'm sure we all made it at some point, that's how we learn.

That's what I thought. But most of us learn before we write a complaint to the manufacturer, write a scathing forum post, and threaten to return the product. 

[csuhi17]

I repeated the above request, a little longer.
I checked its own AWG at 100kHz and 20mVpp with three power supplies.
Powerbank Allpowers USB-c output is 15V.
Its own LiteON power supply.
A Chinese 12V linear power supply built for audio purposes.

LiteON and Linear power supplies have infinite persistence.
That's why the wave got thicker.

+ When I insert the Pendrive, there will be a small error at the low voltage signal.
After attaching the data storage, the error was still visible occasionally.
I could only try it with its own generator, the other one is very noisy for me at low voltage.
Using a USB-HUB, I don't know if the error is permanent or if it interferes with creating a Bode Plot.
I don't have everything to properly test it.

Or it's just me that has this error.

[Mechatrommer]

Using a USB-HUB, I don't know if the error is permanent or if it interferes with creating a Bode Plot.
I don't have everything to properly test it.

that signal should be good enough, you dont bode plot with such low level input signal, the output will be invisible to the scope anyway hence you'll get randomized bode plot. unless you want to test high gain amplifier, but then, dont plug the USB in when you do that. problem solved.

[2N3055]

Using a USB-HUB, I don't know if the error is permanent or if it interferes with creating a Bode Plot.
I don't have everything to properly test it.

that signal should be good enough, you dont bode plot with such low level input signal, the output will be invisible to the scope anyway hence you'll get randomized bode plot. unless you want to test high gain amplifier, but then, dont plug the USB in when you do that. problem solved.

I have no idea what are you talking about. You use signal you need. If you cannot do bode with 20mV signal something is wrong.
It is not problem solved. It is digging head in a sand.

What high gain amplifier? What is high gain to you? 10x?
Why would USB device influence work of a scope?

So you solution to something not working properly is "don't use it so you don't have problem" ?

[csuhi17]

I don't think it's a real case of making a Bode Plot with a 20 mV signal and plugging something in and out of the USB port.

My Micsig scope also has such a problem that when I measure one of my battery chargers with it, which regenerates a 12V battery in repair mode, the touch screen goes crazy.
The error occurs with both Micsigs, but it doesn't bother me.

[Mechatrommer]

I have no idea what are you talking about. You use signal you need. If you cannot do bode with 20mV signal something is wrong.

did you miss the new year fun? is that why you are having bad days? try to be more competent next time cheers.

[pakakezu]

Have you managed to load an arbitrary waveform? If yes can you share an example file?
I spent way to much time with trial and error, because the documentation is a bit thin.

[norbert.kiszka]

Also 924S.
It seems good to me.

can you do me a favor to show low level performance of the AFG, specifically at 100kHz 20mV (pp) at 10mV/div scope setting?

Some time ago I did small research with mine 924S. Looks like it handles output level just with lowering digital signal sent to DAC instead of variable gain amplifier, relays or anything like that.

On lowest levels I saw more noise than signal.

Bad for Rigol, they didnt told about this nowhere 

My idea is to make some simple device with opamp (buffer), switches and potentiometer to set desired level and to have BNCs at front.

[Mechatrommer]

Some time ago I did small research with mine 924S. Looks like it handles output level just with lowering digital signal sent to DAC instead of variable gain amplifier, relays or anything like that.
On lowest levels I saw more noise than signal.
Bad for Rigol, they didnt told about this nowhere 

digital signal are the same, the gain is set by feeding AD9744's FS_ADJ pin and some combination of mechanical relays... to get this signal we need to install 2x ssop8 dual opamp onto DHO800 board (its already there on DHO900 board)

My idea is to make some simple device with opamp (buffer), switches and potentiometer to set desired level and to have BNCs at front.

i did some diy FG years ago using potentiometer, https://www.eevblog.com/forum/projects/ad9850-module-and-dds3x25-dds-based-fg-compared its a bit "touchy", slight movement to potentiometer will get noises, glitches on the output, its ok for your "low tech / hardcore" purpose. but i dont use it anymore since i bought UTG-962. i learnt a lot about AFG circuitry from UTG-962, there are some similarities and differences compared to DHO900S module posted in this forum.

[Randy222]

I have couple soft rubber dome stylus pens, none worked on the Rigol screen, at least not for me.

Hmm, that's odd. When I get home I'll confirm which stylus I tried. I've collected a variety over the years, from the cheapest to somewhat pricey Bamboo and other higher end stylii. I'll try a few different ones tonight and report back the results.

I grabbed several styluses (styli?) from the drawer to try. Every single one worked great on the DHO1074 screen. I couldn't imagine why they wouldn't work exactly the same on the DHO800/900?

I obtained a double-end rubber pad stylus, works ok with some pressure, but can be non-accurate when selecting boxes that are small and close together.

I then got an active stylus, works amazingly well, no BT needed, accurate selections and I don't need to contact screen very hard at all.

https://www.amazon.co.uk/Rechargeable-Magnetic-Universal-Smartphone-Device-Black-Black/dp/B0BZKFT697

[Robaroni]

Every stylus pen I tried worked. I know this is obvious but is your screen locked?

[Randy222]

Every stylus pen I tried worked. I know this is obvious but is your screen locked?

Your Q to me?
I had another rubber ended stylus, it did not work on the 804. I got anoter rubber end stylus, it works, but not very elegantly. The active pen stylus I listed works very well.

[Randy222]

Perhaps not a bug, but definitely some odd logic.

When you go into the Measure menu, why are all the non-selected items turned "on", meaning the icons for non-selected items are highlighted "lit up". That's kinda bad logic. When you select an item, that's when the icon should turn "on".

[csuhi17]

I use the DHO924S's own AWG, with a 20mV signal.
two channels are active CH1 and CH3, the AWG is connected to CH3 (5mV/div), the other is empty.
When I adjust the CH1 voltage scale, between 50mV and 100mV, the signal visibly and measurably shifts by -2mV.

When tested with the other channels, they do not relate to each other in the same way.
In my case, for example, if the signal is on CH3, by adjusting CH1 or CH2, it goes down by 2-3mV, but CH4 does not suppress CH3 as much.

Red REF is when CH1 is active and set to 100mV/div.