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Here is a video from Agilent on this, comparing the 8bit 9000 series Agilent with HiRes to a 12bit ADC Lecroy HRO:
Dave. -
Hi Dave,
excellent video, that says it all!
It also shows that the effect of HiRes-mode can be shown more with a running scope than with a single screenshot.
And: it also shows what I was thinking of when Rosendorfer has asked for a screenshot. A few month ago I had to generate a signal interfered with a small disturbing pulse of a
few millivolts to test the robustness of my signalprocessing algorithm. I've generated the signal with MATLAB and feeded my arbitrary HMF generator with it. Since the HMO scope has got really high quality ADC with low noise level the pulse could be measured - an example, where HR could be used for to remove noise and increase resolution.
Concluding it makes less sense to use standard signals as sine to demonstrate the advantage of HR mode, there have to be more details in the signal to investigate as the video shows exactly.
LeCroy introduced ERES where bandwith is decreased, Tektronix introduced HiRes (Boxcar Averaging). Looking into the manual Rigol and Hameg seem to follow the same concept as Agilent.
Hope all the manufactures try to name the same thing when they use the term "HiRes"
Thanks for the video!
Kind regards
Gunb
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Dear Gunb
I will agree... thanks to Dave for posting Agilent video, it is very interesting...
But again I will come back and ask You nicely again...:
Any chance You could post any screens showing normal vs HR mode..??,
Specially now after Agilent video, where they are claiming/showing that HR mode can bring pretty important and visible improvements to the scope user.
Agilent went far and try to even prove, that 12bit HR mode is as good as real 12 bit ADAC's.!!
They even claim that 12bit HR mode brings SFDR to 74dB..!!!!
Really like it !!!..... It is exactly the way I hope it to be !!!..
All is nice and shiny..
But...
Our only real life(!!) proof is what JimmySte have posted.
And at his screens there is nothing from Agilent's improvements ..
And You have told that it is just right...?? Bit confused...
Wrong test? maybe, Wrong wave form? maybe, Do not know, Not even trying to discus ...
But still the only real thing we have got.
So Is it as at Agilent marketing video or at JimmySte screens...as for now there are pretty different, that is at list "confusing".
And still You are saying nothing left to show... ??
Could be right Your "theory" that it needs some "special kind of waveforms" to "trigger" it working, or high FPS Motion Pictures, to see anything , maybe.
But I'm living in "illusion", question true or not, that 74dB SFDR should be easily seen at FFT's , even with simple sinewave.
Lot have been told.. and lot have been learned, that is very true... but again:
"One picture is worth thousand words".
So ...let me just ask again:
Any chance You could post any screens showing normal vs HR mode..??
Kind Regards
Rosendorfer
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Some screenshots with the DS2102 and another with the DSA815-TG
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The big question, is the hires mode the true signal or the normal mode. noise floor drops but amplitude alters too. Also the time domain signal looks different.
The scope is at 15MHz allmost 3dB different from the SA. But the peaks are all not alike (3dBm is 50% difference in power) is.
I made a small setup tonight for some Hameg FFT pictures. I first had to be sure my signal has the right frequency and amplitude. (using a GPS controlled thunderbird, a HP312B selective voltmeter, two SA's and My HP8640 and my maybe the R&S) They all agreed.
I am gonna use a 10Mhz -10dBm sinewave with -60dBc harmonics. (and probably a pulse too) The Hameg shows the harmonics nice but only decent at 65Kpts and some averaging. So for checking a signal this is usefull but for alighnment not, much to slow.But it was to hot in here so I hope tommorow it is a bit cooler.
Fred -
Hi Fred,
The big question, is the hires mode the true signal or the normal mode. noise floor drops but amplitude alters too. Also the time domain signal looks different.
The scope is at 15MHz allmost 3dB different from the SA. But the peaks are all not alike (3dBm is 50% difference in power) is.
Absolutely right! That's why I mentioned it as a "nice-to-have" feature that will never replace a real 10 bit or 12 bit ADC.
I am gonna use a 10Mhz -10dBm sinewave with -60dBc harmonics. (and probably a pulse too) The Hameg shows the harmonics nice but only decent at 65Kpts and some averaging. So for checking a signal this is usefull but for alighnment not, much to slow.But it was to hot in here so I hope tommorow it is a bit cooler.
Exactly, that's what I'm thinking, too. In particular taking a few neighboured samples together and make one of it is also a kind of loss of information, especially when searching for outliers, i.e. spikes and so on. That's why I do not use HiRes-mode most of the time.
Kind regards
Gunb
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Hi Rosendorfer,
Lot have been told.. and lot have been learned, that is very true... but again:
"One picture is worth thousand words".
I'm working more outside than at home and preparing a special arbitrary signal takes more of my
spare time I'm prepared to offer - sorry, very busied developer.
And what do expect more from my screenshots than Agilent already has shown?
So ...let me just ask again:
Any chance You could post any screens showing normal vs HR mode..??
Kind Regards
Rosendorfer
The signals I have are of confidential use, no way of posting them. If I should find signals when I'm at home
I will post them, but I can't promise to do that during the next weeks.
On the other hand: I always said it's a "nice-to-have" feature that can be helpful for special cases but it will never
replace an ADC with higher resolution. Many people already posted screenshots and most of them revealed that
there will be no real advantage for standard signals - so, take it as it is: it's a feature, nothing else.
As mentioned month ago I would recommend to try to get test unit from a distributor and do your own measurements.
It will show you more than a screenshot and will answer your question if you can use it for your own projects or not.
Especially screenshots are even not a way to show any effects, especially not when "on the fly" calculation is
done as with Boxcar Averaging.
I think of you when I should find time to generate an example
Kind regards
Gunb
Besides: do you understand German? If yes, I could give a link to a technical paper in German (sorry, could not find translations) where HiRes and ERES are explained well.
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Some screenshots with the DS2102 and another with the DSA815-TG
Hi HPerez
Thanks for posting Your screens, having Normal mode with HR mode and even comparison of DS2102 with DS815 is even more I could ask..!!!
Well.....
Could You post some screens showing if at 12 bit HR mode the 74dB SFDR is real number..??
And what about noise floor of DS2102 at 500uV .. how low it actually is and if HR mode does anything to it..??
Thanks again...!!
Rosendorfer -
I posted pictures in the Rigol-Hameg topic (FFT and Hires/normal mode)
Fred -
Hi there,
you all take nice screenshots and press the Hires-button because Rosendorfer likes to see screenshots - no problem with that - but do you really know what you're measuring? What Hires-mode is really doing and what the fundamental basics are behind it?
Honestly I've got the feeling that you're not familiar with time discrete signal processing - no complaint, no accusation.
I mean, it's easy to switch on a scope and produce some nice colorful screenshots, but knowing how it works and what it shows is quite a different thing. And that's why I would argue that screenshots should no be the first chain link but the last.
Let me explain the mistake that I can see in all of your measurements and why you don't see any or only a small difference between normal mode and Hires-mode in most of the screenshots that you already have done.
As already explained to Rosendorfer in one of my previous comments the concept of Hires-mode is to take a few real samples and calculate one to be displayed. This is done at slower timebases where sample rate of the memory is limited and the ADC can provide more samples than can be stored with that speed.
Instead of throwing samples away as in normal mode the ADC runs with its fastest sample rate and takes a group of N samples to calculate 1 to be displayed in Hires-mode. The advantage is that more samples come into play, that the vertical resolution becomes higher depending on the ratio between the maximum sample rate of the ADC and the displayed sample rate and a lower noise floor because higher frequencies are filtered. The disadvantage is a slower signal refresh caused by averaging of the N samples per group and, most of all, that the bandwidth of the signals to be measured becomes lower with each extra bit of resolution!
This method is named "Boxcar Averaging" and the concept is: "don't throw away information, if you can use it".
Where's the limit?
-> It depends on the sample rate the scope is currently working with and that's depending on the selected timebase!
Example #1: you've got a scope with 4GSa/s ADC, the timebase is set to a value that the scope works 4GSa/s, too, that means, it works with its fastest sample rate -> pressing the HR-button has absolutely no effect because there are no samples left to average anything!
Example #2: same scope, but now working with 2GSa/s in normal mode. That means, that the ADC potentially throws every 2nd sample away. Pressing the HR-button now takes exactly 2 real sampled values and calculates exactly 1 displayed sample from it.
Example #3: only to make it crystal clear: My HMO2524 has got an ADC of 2.5GSa/ at max. When I choose a timebase where it samples with 625MSa/s, the ratio is 2.5GSa/s to 625MSa/s equals 4. It means that 3 of 4 samples are thrown away in normal mode. Pressing the Hires-button now takes all 4 samples and calculates the average "on the fly". The result - 1 sample - appears in screen then.
No you might ask: and what all of this has to do with HIGH RESOLUTION???
Well, as mentioned many times the algorithm behind that is the "Boxcar Average" that can be implemented as a simple FIR filter algorithm on DSPs, microcontrollers, FPGAs ....
It's a so called one pole filter that takes N samples for 1 average value.
One effect is that the gain of resolution follows the formula: 0.5*log (base 2) N - VERY IMPORTANT to understand!!!
This formula tells you how many extra bits you can win the more N samples are taken into account to calculate your average!
Example #4: If you sample with the maximum sample rate of your scope's ADC, exactly 1 sample is taken into the filter algorithm, i.e. N=1, that is: 0.5*log (base 2) 1 = 0!!! No gain of resolution!
Example #5 :If you sample with half of the ADCs maximum sample rate, i.e., N = 2, the formula says: 0.5*log (base 2) 2 = 0.5!!! You will win 0.5 extra bits of resolution, that is 8.5 bits instead of physical 8 bit
Example #6: If you sample with a quarter of the ADCs maximum sample rate, that leads to 4 samples per group, i.e., N=4, the result will be 0.5*log (base 2) 4 = 1!!! No we're at 9 bit resolution.
Do you understand now why you don't see any difference when you press the HR-button when sampling with the ADC's maximum sample rate?!?!? Or there's nearly no effort if using half of it?!
And that's not all!
One disadvantage of the Boxcar average - the Hires-mode - is that it works as a one pole filter where the -3dB bandwidth depends directly on the displayed sample rate.
It follows the 3 db bandwidth limit: 0.44 x displayed sample rate
So, if you're scope has got a 2.5GSa/s ADC, the display shows a sample rate of 625MSa/s depending on the chosen timebase, the filter limits the maximum signal frequency to 275MHz with a resolution of 9 bit.
If you really want to see the difference, you should follow these guideline:
#1: calculate the ratio between the maximum sample rate and the actual displayed sample rate and assign it to N
#2: set it into the formula: 0.5*log(base 2) N and you'll get the extra bits of resolution
#3: depending on the displayed sample rate calculate the limiting bandwidth of 0.44 * sample rate and investigate if your signal frequency is below that
#4: for demonstration use signals where noise is interfering a small vertical detail to see the difference
#5: then take a screenshot to demonstrate the difference.
--> my explanations show:
- why all manufacturers speak about "up to x bits" extra resolution
- why it never can replace an ADC with real higher resolution
- why it absolutely makes no sense to post screenshots without understanding these fundamental basics, otherwise it's nice & colorful only.
- and most important, that High Resolution is not a constant for any chosen timebase. Now you can calculate yourself how to adjust the scope to reach it.
Beside that, look into Rigol's datasheet, they tell more precise than Hameg at which timebase and sample rate the resolution is.
And: I've also the DSA815 but comparing FFT with a real analyzer can be tricky in case of non-periodic signals and knowing nothing about smearing effects and how windows have to be used. But that's quite a different story
Hope it's helpful for further measurements
Kind regards
Gunb
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Nice explanation. I know a lot about analog scopes and SA's and how to measure, but I'm digital disabled. So nice to read more about this.
While making the pictures I noticed what you told about samplerate. And also that a bigger ratio made a bigger difference but i was measuring 10 and 100 MHz. I could not get a higher ratio and keeping useable resolution.
But according to your explanation I do not understand why the 2nd and 3td harmonic are way of, while the higher harmonics in hires mode were closer to what they should be. That should the the other way around not ?
But the main problem is both methods do not give the right results. Hires result is a small differense if it changes samplerate but it does not seems to give more accurate results, hut other results.
Only the First harmonic is rather correct. Very good considering I used -40 dBm so we are talking about a fault from a few uV's and becausec how FFT works I understand higher harmonics are difficult in this case, we talk about very very small signals buried in a big signal. A harmonic of -80 dBm is a voltage a scope in theory can not even measure.
So considering that it is still a rather good achievement, but from an instrument we want usable accurate results, not wrong results we like because they are clever made or the pictures look great. ( i placed a HP SA picture as compare and measured the signal on serveral other ways like a HP selective voltmeter and an other SA)
The reason I made the pictures was first for myself to see if FFT on the Hameg is a usable function because i found it rather useless on my DS1102e. And i must say i'm impressed by the low noisefloor and i think results are usable to check an oscillator on harmonics for instance. But it is often to slow to make adjustments ( but i use a VNA for filters and check output on the analog SA)
I checked the hires mode only because Rosenberger asked in the hope someone could comment them.
Fred
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Hi PA4TIM.
I think, it's absolutely legal to make screenshots, didn't want to criticise thatI could not get a higher ratio and keeping useable resolution.
But according to your explanation I do not understand why the 2nd and 3td harmonic are way of, while the higher harmonics in hires mode were closer to what they should be. That should the the other way around not ?
#1 Higher resolution: I haven't studied all the details of your measurements, only a rough view. But you should consider not to forget the manufacturer's datasheet. They restrict the maximum of resolution opposed to the formula. Hameg says "up to 10bits" for my HMO2524, Rigol "up to 12bits" for my DS4012. The formula is open for everything
#2 Harmonics: First of all I my explanation did not consider FFT at first place. I will have to study the results first and think about it. Hires-mode is not introduced for FFT in the first place but to get more details from signals. But indeed it should work with FFT, too.
Kind regards
Gunb -
Anyone good with audio/SNR-testing: is my DS2072 is performing good data capture?
Interesting question here: how well can DS2072 perform at analysing Audio system noise -
I'm aiming for better than 80dB SNR 70Hz - 20kHz (which I reckon is 40dB in terms of the volts datapoints).
Here's the resulting Volts spectrum, performed on the data captured by the RIGOL - see attached JPG file.
This test is a simple 2-level, 2-tone test:
Big signal at 1kHz PLUS second v. low level signal 250Hz <300uV... straight into Ch1 of DS2102.
Use PC to grab 1400 points - one display memory - then look at spectrum (FFT using PC software).
Check spectrum as a means of recording real system SNR.
I love what this scope can do for the price - maybe it can help me here too.. I'd really appreciate views from people who've done decent quality audio testing and know what tests are out there...
Does this get me towards a decent audio system SNR-test method?
Many thanks!
Dave.
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Love the review but one thing I find disturbing is that so many of the features are trial features and are disabled soon after you buy it. How much money does it cost to get the average feature re-enabled? Is there a webpage that list the prices?
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Last time I checked the price for DS2000 decodes (SD-DS2) was £157
Gives you RS232, I2C, SPI - this was from the RIGOL-uk sales engineer folks. See http://www.rigol-uk.co.uk/rigol-ds2000-series-digital-oscilloscope/
They got me some useful extra help on working with data (see back 2-posts).
PLEASE - audio gurus look at my SNR results - PLEASE could you give me an honest view on my test results: SNR spectrum is pictured 2 posts earlier?
My displayed sample rate was around 100kSa/s for the data above. (I've read Grunb's excellent notes and I can see why slower rate might cause HF-roll-off, but using the 0.44 rule I think I'm OK with this rate for my test to 20kHz, yes??)
Thanks,
Dave.
P.S. The machine was a DS2072 (not a 2102 as stated above - was thinking of upgrading my machine and had 200MHz DS2202s on my mind too!) -
Here you can see the performance of the scope in XY mode:
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Hello everyone!
I recently found the EEVblog and this forum, and I must say it is excellent! The product reviews and forum comments from end-users is a tremendous resource, especially for EE hobbyists like myself who are researching for a nice capable 'scope, and trying to get great value for money. I've seen there are a number of cheap Chinese DSO's on the market, and so it is important to know the good from the bad when making a purchase choice.
I've been researching and reading for a few days through these pages and the Rigol DS2000 series are looking mighty nice! I love that big screen, and other features that have been previously mentioned, and the options seem reasonably priced (seems like you can't escape paying for software unlock these days...), especially compared to Agilent and others. I've read there are some firmware bugs on the DS2000, and Dave's recent review (EEVblog #369 - Rigol DS2000 Oscilloscope Playing Around), highlights a few usability issues, but Rigol is not Agilent, and so while I hope for the best, I'm willing to accept a few "issues". But, from my reading, the DS2000 looks great on paper and from peoples opinions the general consensus seems to be that its excellent value!
So, being keen on this 'scope, I'm wanting to hear a little more of its short-comings before I commit to it. I wonder if we can hear from users about the "dual time base" feature, which in Dave's video blog on the DS2000 he shows by recording a waveform and then trying to zoom in...but he can't get it working properly. In fact, it looks like a major problem and the scrolling of the waveform doesn't appear to work at all. Have any of the users here (JimmySte, playfsx, ...) been able to try this out? I'd love to know whether this feature is broken, as seems to be the case in Dave's video, or whether there is something else needed to get it working.
Thanks for your comments folks!
Cheers! -
I really impressed with the UI and resolution. Just wish it was 4-channel. I just can't see upgrading from a rigol ds1052e to another 2-channel scope for 3 times the price.
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I have also this DS2202 scope. I have not this time base issue about what Dave told, but I have the old firmware. Maybe this issue is the problem of the new firmware.
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I've read there are some firmware bugs on the DS2000, and Dave's recent review (EEVblog #369 - Rigol DS2000 Oscilloscope Playing Around), highlights a few usability issues, but Rigol is not Agilent, and so while I hope for the best, I'm willing to accept a few "issues". But, from my reading, the DS2000 looks great on paper and from peoples opinions the general consensus seems to be that its excellent value!
So, being keen on this 'scope, I'm wanting to hear a little more of its short-comings before I commit to it. I wonder if we can hear from users about the "dual time base" feature, which in Dave's video blog on the DS2000 he shows by recording a waveform and then trying to zoom in...but he can't get it working properly. In fact, it looks like a major problem and the scrolling of the waveform doesn't appear to work at all. -
Thanks, EV, for contributing your experience with the DS2202 'scope. From what you say, it seems likely the bug was introduced by the new firmware (when correcting the X-Y mode issue Dave talked about in his video).
I'm thinking it would be valuable to compile a list of DS2000 firmware versions, and the reported problems from users. The DS2000 series are relatively new so I doubt there are many firmwares available yet, but in the long run it would be a good resource for people when considering firmware upgrades. What do users think about an "RIGOL DS2000 Series Firmware" thread on this topic?
On the topic of firmwares, it seems the only way to get new releases is by emailing RIGOL technical support. Is this true? It seems a slow/inconvenient way to get updates... Is there an "automatic check for firmware update" available on the scope? -
So, being keen on this 'scope, I'm wanting to hear a little more of its short-comings before I commit to it. I wonder if we can hear from users about the "dual time base" feature, which in Dave's video blog on the DS2000 he shows by recording a waveform and then trying to zoom in...but he can't get it working properly. In fact, it looks like a major problem and the scrolling of the waveform doesn't appear to work at all. Have any of the users here (JimmySte, playfsx, ...) been able to try this out? I'd love to know whether this feature is broken, as seems to be the case in Dave's video, or whether there is something else needed to get it working.
I can also confirm that the same problem occurs in regular dual timebase mode when STOPed, not just in waveform capture/replay mode (a.k.a segmented memory).
Dual timebase works fine in regular updating mode.
But I have been assured that this is not normal, so the verdict is still out, I'm waiting on a response.
Dave. -
I just bought a Rigol DS2072 to replace my 35 year old Phillips PM3212 that just died. I've been evaluating the High Res mode and it does work. I programmed my computers 16 bit DAC to produce a sine wave with a tiny 0.7 LSB blip on it, much like the Agilent video posted earlier. The Rigol could easily resolve the blip in High Res mode despite the fact that it was only 0.7 LSB of the 8-bit ADC. The first figure (assuming it will allow me to attach images) shows the High Res trace blown up. This trace was taken 100 mV/div and 2 ms/div and blown up post acquisition to 5 mV/div. Of course, for a repetitive signal you could also just turn up the sensitivity to 5 mV/div and hunt for the blip with the offset and time/div and this is shown in the second figure.
Of course, the extra resolution you get from boxcar averaging doesn't mean much if the DNL (differential non-linearity) of the ADC is not good, so I used the ramp and histogram method to measure DNL. The results are that it's pretty good: only +-0.15 LSB.
Finally I measured the noise on the 500uV/div scale as 80uV RMS in Normal acquisition mode and 40uV RMS with the High Res mode, both with the 20MHz BW limit on. With the 20MHz BW limit off and Normal mode I got 100uV RMS. These are all with the input shorted with a 50 ohm terminator.
PS remember when calculating LSB remember that the 8 vertical divisions are not the full range of the ADC; it's actually 10.24 divisions with headroom off the top and bottom of the screen plot region.
[Edit: replaced HP with Agilent- shows hold old I am.]
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Hi TP - thanks for your interesting info. You might want to move (or repost) it to one of the newer threads we're using for discussing features, bugs, and software for the DS2000 series:
https://www.eevblog.com/forum/reviews/first-impressions-and-review-of-the-rigol-ds2072-ds2000-series-dso/
https://www.eevblog.com/forum/projects/software-tips-and-tricks-for-rigol-ds200040006000-ultravision-dsos/ -
Hi TP - thanks for your interesting info. You might want to move (or repost) it to one of the newer threads we're using for discussing features, bugs, and software for the DS2000 series:
https://www.eevblog.com/forum/reviews/first-impressions-and-review-of-the-rigol-ds2072-ds2000-series-dso/
https://www.eevblog.com/forum/projects/software-tips-and-tricks-for-rigol-ds200040006000-ultravision-dsos/
Thanks. I was responding to Rosendorfer who seemed interested in a screen shot that shows if High Res mode actually works. The DNL measurement was also relevant to that question. Should I also post in the "first impressions" thread? -
Should I also post in the "first impressions" thread?
Yes, I think your tests, measurements, and conclusions would be very pertinent there. I haven't had any time yet to explore the Hi-Res option of the scope.