Rigol DHO804 Test and Compare Thread

[Fungus]

Oh! So you really believe the DS4000 would have performed better if we'd measured it at 10 divisions offset instead of just three?

No, I want to know how all the others perform at 10 divisions, just like we're applying to this $399 'scope to achieve a couple of pixels of distortion.

I demand a graph of number of pixels vs. price in dollars from 3 to 10 divisions of offset. It's the only way to form an unbiased opinion.

[2N3055]

What I tested is following (and I suggest you test the same on Rigol):
- same demoboard sine 50 Hz non filtered.
- Input in DC mode.
- position signal that you look at top of sine. (5 ms/div).
- try at 200, 100, 50 mV/div ( I don't know the offset range of top of my head.).
Look for distortion...
Hint: once you roughly get where it starts distorting, set vertical to fine for more precise point..

I had done this with the "lower peak" of the sinus, because from 100(or was it 50)mV the rigol allows an offset of +/-1V (above this it is 8V).
When I found nothing, I shortened the time base to 500µs, see picture.

Yes that is distortion....
Complete sinewave is "assembled" from straight vertical and horizontal segments...
You need to go to 50, 100 or more mV/div until there are no angled segment at all... Only clean steps...
That is point where no distortion occurs..

[Martin72]

For the siglent, the upper area would not be a problem in terms of offset, but I also triggered on the lower tip for better comparison.

[Performa01]

Of course word should have gotten around by now that we must not overload the inputs of modern DSOs – or any scope with split path input buffer, which are almost all scope designs today (Picoscope 4262 is one of the feew exceptions).

Just as a reference, here are tests with the Siglent SDS2504X HD, similar to what TurboTom did:

First the Overload test. 10 kHz triangle, 6 Vpp amplitude, viewed at 50 mV/div with an additional offset of 1.5V:

SDS2504X HD_Ramp_OVL

Now the offset challenge. A 350 mVpp triangle is fed into channel 2 as reference. Channel 4 gets a copy of that signal with 6 V DC offset. No worries, of course.

SDS2504X HD_Ramp_Offset

Fnally the question, why the heck does everyone always want to overload the oscilloscope input? Why not just use zoom if we want to inspect a signal in more detail?

The last screenshot shows a ten times zoom into the signal (5 mV/div in the zoom window) which has essentially the same effect as the overload method, just with the difference that we can feel better because we stayed away from unspecified territory.

SDS2504X HD_Ramp_Zoom

People will now bitch: “oh, we cannot compare the cheap rigol to an immensely expensive Siglent!”

First, there’s no point in having a scope advertised as 12 bits when its performance is just not there, no matter how cheap it is.

Second, The Siglent SDS1000X HD will perform just as well as the 2000 (except for the bandwidth and MSO option) and it will most likely be very affordable.

[ebastler]

The Siglent SDS1000X HD will perform just as well as the 2000 (except for the bandwidth and MSO option) and it will most likely be very affordable.

Here's hoping... I have actually decided to wait for the SDS1000X HD to become available. It will obviously outperform the DHO 800/900 in many respects, but whether I can justify the extra cost to myself will depend on the price tag. Looking at Siglent's recent tweaks to the positioning, I'm afraid it will be closer to 3x the DHO914 than 2x...

[Martin72]

But then the dho800 surprises you with some gadgets:
It has not only a frequency counter, but also a dvm function at the start.
And zoom is also included, albeit somewhat hidden.
I think that's great for a 500€ scope.
And take a closer look at the dvm infobox, what else can be read there.
I find it.....interesting.

[Fungus]

Fnally the question, why the heck does everyone always want to overload the oscilloscope input? Why not just use zoom if we want to inspect a signal in more detail?

Beats me...

The DS1054Z distorts a lot if you switch to fine vertical range adjust (push the vertical scale knob) and crank it up to maximum.

The fact that you could just use the next higher range instead didn't stop several threads about the "problem".

there’s no point in having a scope advertised as 12 bits when its performance is just not there, no matter how cheap it is.

You're saying there's no point at all in owning one of these 'scopes?

This 'scope is trying to replace the DS1054Z, not the SDS2000HD. Will it help you to see the value if I grab a sharpie and cross the "12bits" off the front?

[Fungus]

And zoom is also included, albeit somewhat hidden.

You only just found it? You can zoom with a setting in the "H" menu.

There's also an option in "setup" to make the timebase knob do "zoom" when you push it.

(but it doesn't seem to remember that setting when you power off  )

[Martin72]

There´s no dedicated zoom button on the front (like the dho4000 have), so I thought the 800 did not have it.
Then I´ve stumbled over it in the manual, the setup menu...

[Fungus]

It took me a while to find it, too, but it has the zoom function you'd expect:


It's good for serial decoding on long bursts of data. Drag the zoom window left/right to decode different packets.

It can also zoom out properly after you STOP it. 


There's an option for zoom in the 'H' menu at the top. I assume they put it there for when you're using a 50" touch screen in board meetings.

[Martin72]

(but it doesn't seem to remember that setting when you power off  )

I just turned the scope back on, zoom is still there because last state - but button is back to "fine"....
If you go to the horizontal menu, you will see that both modes are active (zoom and fine)...
Small bug, because last state should be completely last state.

[nctnico]

It looks like somebody at Rigol was sleeping during the lecture about significant digits.

[iMo]

It looks like somebody at Rigol was sleeping during the lecture about significant digits.

They create a platform for future enhancements, like a 24bit ADC.. 

[Martin72]

This is a three digit DVM with the same bandwith(aha...) like the one in the dho 900 series..
I had connected my DMMplus reference earlier and measured 5DC, 5Vac 100Hz and 10 Khz with accurate duty cycle.
The nice measure window unfortunately does not apply to the counter and DVM function.

[Serg65536]

Rigol DHO800 and DHO900 don't have a PROPER ZOOM function.

That's because you can't move the waveform more than vertical offset allow. So you can't use 12 bit resolution outside ±1 V range because of this issue.
2^12 = 4096, so to fully zoom in on 5 V/div with offset range of ±100V you have to switch to the 1 mV range that has ±1V offset only. So more than 99% of the capture range is outside the zoomable area.
Here are offset ranges:
0.5, 1, 2, 5, 10, 20, 50 mV/div - ±1 V offset
100, 200  mV/div - ±8 V offset
500 mV, 1, 2  V/div - ±20 V offset
5, 10  V/div - ±100 V offset

[Circlotron]

Whiny fans are just that: instead of producing wideband noise, they make sound that has peaks in spectrum that allows our ear to recognize tones.
If you have any tone between 400-4000Hz where our ears are most sensitive, you will hear annoying whine (tone). Simple as that. It can also be at other frequencies, but between 400-4000Hz we are very sensitive.

As long as you do it the same for all of them you will have good relative measurements. Then compare spectrum to how it sounds to you and you will quickly find what the "whine" is all about.

I did just that to few devices. One good example of device that is not completely silent but has very "noise like" sound is Keysight MSOX3000T. Just a whooshing, not very silent but with no distinguishing tones so no whining.. Excellent acoustic design.

Best one is, of course, Siglent SDS2000X HD. Pretty much completely silent. Large, low speed fan, and cooling based on low pressure/low speed airflow volume.
Siglent SDSD6000H12 Pro OTOH is quite louder. But that one needs to expel much more thermal energy out of the case... It is still not annoying because there are no large peaks inside so you forget about it, but after few hours, when you switch it off you suddenly realize how quieter the room is. Of course, that is my very quiet lab, in open space office not so much.

DHO800 has miniscule fan that pretty much guarantees whine and noise by itself. Offending tones will be easily measured.

Fans with evenly spaced blades are more likely to whine. The fan blades on a car alternator are unevenly spaced for this reason. Gives a spread spectrum effect so there won’t be sound concentrated at one frequency.

[Serg65536]

In the "Vertical" window you can change the "bias" value.
But it's intended use, according to the manual, is for zero out the offset of the channel only.
BTW using bias at 100 and 200 mV/div gives OUTPUT VOLTAGE from -40 mV (for -8 V bias) to 60 mV (for 8 V bias). Yes, the scope can generate output voltage at its input!!
For the 500 mV, 1, 2 V/div ranges output voltage range is -1,7...3.5 mV.
So don't try to move you waveform with the "bias" field!!

[Fungus]

the scope can generate output voltage at its input!!

Ummm... yes. It wouldn't be able to calibrate itself without that feature.

Rigol DHO800 and DHO900 don't have a PROPER ZOOM function.

Do you have an oscilloscope that can do better?

[csuhi17]

the scope can generate output voltage at its input!!

Ummm... yes. It wouldn't be able to calibrate itself without that feature.

Rigol DHO800 and DHO900 don't have a PROPER ZOOM function.

Do you have an oscilloscope that can do better?

SDS2354X HD, if I saw it correctly, it's quite impressive.

[Fungus]

Rigol DHO800 and DHO900 don't have a PROPER ZOOM function.

Do you have an oscilloscope that can do better?

SDS2354X HD, if I saw it correctly, it's quite impressive.

OK, so go get one of those instead of one of these Rigols...

[csuhi17]

I'm sorry, I didn't mean to be rude, I just saw that you compared the +4000 USD scope to this 300 USD cash.
I also ordered one of these...

[2N3055]

the scope can generate output voltage at its input!!

Ummm... yes. It wouldn't be able to calibrate itself without that feature.

What are you talking about? In what opposite universe channel offset settings is supposed to generate OUTPUT voltage on INPUT BNC of the scope...?
You better take a meter and measure if your scope has that problem or it is an error in measurement or some kind of misunderstanding....

This can be connected to offset/AWG problem Tom had..

P.S. Even those 70µV you see are generated by that being non-shielded measurement, all kinds of unwanted thermocouples and multimeter zero offset

[2N3055]

Rigol DHO800 and DHO900 don't have a PROPER ZOOM function.

Do you have an oscilloscope that can do better?

SDS2354X HD, if I saw it correctly, it's quite impressive.

OK, so go get one of those instead of one of these Rigols...

Rigol could have implemented that. It is a software thing. No BOM price attached.
And even the DHO4000 that is also expensive in comparison to dho800/900 does not have that.

[Fungus]

the scope can generate output voltage at its input!!

Ummm... yes. It wouldn't be able to calibrate itself without that feature.

What are you talking about?

Calm down and count to 10 before posting.

 I'm referring to the "offset" part of the "offset+gain amplifiers" that ALL oscilloscopes have.

(Hopefully Mr. Red Ink is referring to the same thing)

It is a software thing. No BOM price attached.

I'm fairly sure offset amplifiers are hardware.

[tautech]

the scope can generate output voltage at its input!!

Ummm... yes. It wouldn't be able to calibrate itself without that feature.

What are you talking about?

Calm down and count to 10 before posting.

 I'm referring to the "offset" part of the "offset+gain amplifiers" that ALL oscilloscopes have.

(Hopefully Mr. Red Ink is referring to the same thing)

It is a software thing. No BOM price attached.

I'm fairly sure offset amplifiers are hardware.

You don't seem to get it.
Vertical zoom is a SW special feature and little to do with vertical offset limits.