Rigol DHO804 Test and Compare Thread

[Martin72]

A short clip about using the UI, vertical adjustments, with a clear "winner".

[sorenkir]

Is it possible that this messed-up Flat Top window has been a Rigol tradition forever? My old DS1054Z shows very similar "leaky" spectral lines when using the Flat Top window. No easy way to swap out the window function on that scope, I'm afraid...

It seems that the MSO5074 has the same "traditional" Flat Top window:



Michel.

[Randy222]

Hi,

Just for fun, the boot times of the three little pi...no, scopes.
I was comparing something else and thought to myself, oh, just make a clip.
I personally don't care about the boot time, I hate it with multimeters and recently also with power supplies.

The 804 I got with 01.02 firmware takes 54sec to get to the ready-for-use state.
I find it odd it boots up to an active CH1. IMHO it should boot to no active channels.

[Martin72]

I wanted to measure the noise level, today I prepared something, but I have to realise that it's too loud in my study during the day.
So I'll do it all again(with different settings like more resolution) in the later evening or night, but I'll show the first results here anyway.
As I said before, the DHO804 is not the loudest scope I have here...
It's actually the quietest of the three.
(Software: REW, Microphone: UMIK-2, calibrated, 96khz samplerate)

[core]

I wanted to measure the noise level, today I prepared something, but I have to realise that it's too loud in my study during the day.
So I'll do it all again(with different settings like more resolution) in the later evening or night, but I'll show the first results here anyway.
As I said before, the DHO804 is not the loudest scope I have here...
It's actually the quietest of the three.
(Software: REW, Microphone: UMIK-2, calibrated, 96khz samplerate)

A very good initiative. Thanks for sharing!
The more devices you can measure, the better chance we have of comparing to something we already have.
If you could find an MSO5000, SDS2000X Plus and a DHO1000, it would really fill in a picture of the noise of the devices we currently use. I suspect you will also measure for the SDS2000X HD 

[Martin72]

Hi,

At the moment I have SDS1104X-E, DS1054Z, DHO804, SDS2504X HD and SDS2104Xplus here...
Maybe tonight or tomorrow in the early morning I´ll make some measurings.

[Martin72]

Not tonight, half an hour ago...
It's hardly going to be any quieter in the room, I might look for a quieter place - but that wouldn't be practical and that's really the point.
In addition to the actual measurement distance (0.5m away, 1.2m high (ear height when sitting)), I also made recordings in the immediate vicinity of the fan.
This not only blocks out the ambient noise, but also allows you to see the character of the fan in question.
I also took measurements on the SDS2504X HD - somewhat unfair, because unlike the other four scopes, my HD no longer has the original fan - but it wasn't any louder.
An integrated fan controller is quite nice.

[Performa01]

I also took measurements on the SDS2504X HD - somewhat unfair, because unlike the other four scopes, my HD no longer has the original fan - but it wasn't any louder.

These measurements also show how meaningless the dB figures of the "far-field" measurements are, as they indicate only 2.21 dB difference between the SDS2504X HD and the DHO804. Since I know from experience that the SDS2504X HD is barely audible even with the original fan, while on the other hand some people have complained about the fan noise of the DHO804, it's quite obvious that the actual difference must be much more than that.

Looking at the spectra confirms this very clearly: two dominant tones, ~35 dB @ 64 Hz + 34 dB @ 590 Hz for the DHO804 and only one dominant tone 32 dB @ 49 Hz for the SDS2504X HD. Since the human ear is much more sensisitive at medium frequencies like 590 Hz than at low frequencies like 49 Hz, it is clear that there must be a difference like day and night.

And the near-field measurement confirms this very nicely: 20 dB quieter and no dominant frequency for the SDS2504X HD is exactly as expected.

Even the comparison of the "veterans" is quite interesting - I never would have guessed that the DS1054Z is such a hell-machine and manages to be another 6.73 dB louder than the already loud SDS1104X-E...

[ebastler]

I think that the noise spectra are hard to interpret and compare in general. Predicting from the spectra how annoying a particular fan sound will be perceived will only be possible with a lot of experience, at best.

My preference would be short audio recordings, to allow for a comparison of the "subjective" effect of each scope's fan noise. If a set of recordings can be made with the same microphone gain setting for a range of instruments, any user who has one of those instruments as their local reference could easily compare and get a good impression what noise to expect from the other devices.

[Martin72]

These measurements also show how meaningless the dB figures of the "far-field" measurements are, as they incicate only 2.21 dB difference between the SDS2504X HD and the DHO804

That's why I recorded the spectrum and not just the numerical SPL value.
Whereby +3dB more already means a doubling of the volume and in some frequency ranges of the spectrum this is easily exceeded.

[Performa01]

I think that the noise spectra are hard to interpret and compare in general. Predicting from the spectra how annoying a particular fan sound will be perceived will only be possible with a lot of experience, at best.

Why do you think so? I happen to have some experience in the audio field, but even without that the fundamentals of human hearing together with a look at the Fletcher-Munson curves would be enough to interpret an audio spectrum correctly:

https://en.wikipedia.org/wiki/Equal-loudness_contour

We are talking about SPL (sound pressure levels) between 30 and 40 dB here. The threshold of human hearing at 50 Hz is at about 42 dB.

So why should I not be able to safely state that 32 dB @ 49 Hz is inaudible for the mere mortal?

34 dB @ 590 Hz on the other hand is equivalent to at least 30 phon – quite audible, independent from the age of a person.

[ebastler]

I think that the noise spectra are hard to interpret and compare in general. Predicting from the spectra how annoying a particular fan sound will be perceived will only be possible with a lot of experience, at best.

Why do you think so? I happen to have some experience in the audio field, but even without that the fundamentals of human hearing together with a look at the Fletcher-Munson curves would be enough to interpret an audio spectrum correctly:

https://en.wikipedia.org/wiki/Equal-loudness_contour

We are talking about SPL (sound pressure levels) between 30 and 40 dB here. The threshold of human hearing at 50 Hz is at about 42 dB.
So why should I not be able to safely state that 32 dB @ 49 Hz is inaudible for the mere mortal?
34 dB @ 590 Hz on the other hand is equivalent to at least 30 phon – quite audible, independent from the age of a person.

"Inaudible" is fine, of course, and knowing or looking up a threshold for that is no problem. Having a good feel for how much more noticeable +3dB are (at various absolute levels) may already be less clear.

But what I was mainly thinking about are deviations from white or pink noise. We frequently read descriptions of (and complaints about) noise that is perceived as "whiny", "high pitched", "with a clicking noise" etc. To recognize the signatures of such noise components in the spectra is where I think a lot of experience is needed. And to assess from looking at the spectrum how obnoxious the noise will sound is probably impossible, since it is a rather subjective perception anyway.

[Performa01]

"Inaudible" is fine, of course, and knowing or looking up a threshold for that is no problem. Having a good feel for how much more noticeable +3dB are (at various absolute levels) may already be less clear.

Quite clear if one sticks to the fundamentals: an increase in 10 phone (above some 40 phone) is equivalent to a perceived doubling of the sound volume. Once again, the Fletcher-Munson curves help us to find the correlation of SPL and the loudness measured in phon. There’s usually no scaling, i.e. a 10 dB increase in the phon measure will correspond to 10 dB more SPL, but there is a frequency dependent shift in sensitivity.

But what I was mainly thinking about are deviations from white or pink noise. We frequently read descriptions of (and complaints about) noise that is perceived as "whiny", "high pitched", "with a clicking noise" etc. To recognize the signatures of such noise components in the spectra is where I think a lot of experience is needed. And to assess from looking at the spectrum how obnoxious the noise will sound is probably impossible, since it is a rather subjective perception anyway.

I don’t even believe that it’s that subjective. Yes, white (and even more so pink) noise should be quite unobtrusive – and it shows, since it’s used for medical purposes in noise masker systems for tinnitus treatment.

What is more annoying are dominant frequencies, and these in turn all the more so as closer they are to the maximum sensitivity of the human ear, i.e. 3 kHz.

Even more annoying are low frequencies (which would be inaudible themselves) with very high harmonic content that is audible (“ticking sounds”).
Or any form of frequency modulated dominant tones (“whining noise”). Here it might be a little subjective indeed, which one are perceived as more annoying.

And for all types of unwanted sounds and noises it is clear that they are all the more annoying the louder they are.

[core]

The noise spectrum plots are very interesting. Since local conditions cannot be easily compared, measurements taken very close to the fan may be most useful.

Personally, I would not change a fan without knowing that the new one does not have at least the same airflow or without comparing the measured temperature with a thermal imaging camera.

Also, the average temperature measured by a speed controller added later to a default installed fan doesn't tell much about certain hot spots like local power supplies, which can get too hot without a minimal airflow.

[Fungus]

Personally, I would not change a fan without knowing that the new one does not have at least the same airflow or without comparing the measured temperature with a thermal imaging camera.

These have a single heatsink and can show their internal system temperature on screen. Thermal camera isn't really needed.

[Martin72]

If you take this a bit more seriously, I would want to capture the hotspots with a thermal camera - before replacing the fan.
Most people want to install a fan externally, so it would be a good idea to monitor the temperatures with the camera.
Unless there are enough internal sensors available that can be displayed.
Is this the case and how do you do it?

[ebastler]

Unless there are enough internal sensors available that can be displayed.
Is this the case and how do you do it?

You mean the Utility > Self Check > Board Test display? (If the manual is correct and it's in the same place as with the DHO1000.)

[Martin72]

Aha, will check this...Now.

[Martin72]

That's a bit meagre, actually too little.

[Martin72]

That was a good one. edit post was removed from user
Here is an example of how to do it right, if you are already doing it.

[Fungus]

Aha, will check this...Now.

You didn't know??

That's a bit meagre, actually too little.

There were some thermal images posted earlier showing the CPU is the hotspot so that should be enough info with this big uni-heatsink.

[Fungus]

That was a good one. edit post was removed from user

I was just rewording it carefully because my loyal fan club is out in force today.

[Martin72]

Let's stay reasonably objective here, that helps everyone much more than anything else.

There were some thermal images posted earlier showing the CPU is the hotspot so that should be enough info with this big uni-heatsink.

Let's see if I feel like voiding the warranty and getting an impression with my Flir.

[Fungus]

Let's see if I feel like voiding the warranty and getting an impression with my Flir.

You really need to do it without the fan to find the true hotspots... 

Somebody did a simulation, you could verify it:

https://www.eevblog.com/forum/testgear/hacking-the-rigol-dho800900-scope/msg5189571/#msg5189571

[ebastler]

That's a bit meagre, actually too little.

Indeed, that's less than I expected. The DHO1000 dialog shows much more info.