REVIEW - Rigol DS2072 - First Impressions of the DS2000 series from Rigol

[Leon]

I've ordered a 2102, it should arrive pretty soon.

[devitrify]

I recently received our DS2102 scope -- it's my first digital scope, and it's a huge step forward over my old circa 1980 HP!

We plan to use it for our high school robotics team.  I hope to use the decoding functions for our CAN bus, and I am pleased to see some great demos of this capability already posted.

I've run into a few bugs, and have contacted Rigol who says they are known but that there is no firmware update released yet.  You can see in the attached image, a bug where all the test data is wrongly shown as identical.

My DS2102 scope shipped in May 2013 with:
   Firmware:00.01.00.00.03
as reported in the file NewFile1.txt that I downloaded onto a USB flashdrive.

Though maybe not a bug, I noted that when I download a waveform onto a USB drive, the resolution is reduced below that displayed on the scope.  For example, at 2 V/div, the resolution in the downloaded file is 0.080V.  For a full screen deflection of 16V (= 8 x 2V/div ), the # of steps is 200  ( =16V / 0.080V).  I'll have to explore more to see if it is possible to download at higher resolutions.

In spite of the bugs, my first impressions of this scope are very positive!

[Hydrawerk]

Those Rigols are feature rich, they have good hardware, but because of those bugs
  I would never trust this scope.    Anyway, when they finally make a good firmware without bugs, it will be a good scope.

[marmad]

I've run into a few bugs, and have contacted Rigol who says they are known but that there is no firmware update released yet.  You can see in the attached image, a bug where all the test data is wrongly shown as identical.

This bug was just introduced in the last version of the FW - and has already been fixed in the upcoming version. It is in our bug list on the opening page:
Re-selecting two or more measurements from the left-side menu after booting-up can cause some of the measurements to be incorrect.
Current workarounds include:
Only select one measurement for screen bottom
or - use 'Display All' (with 0 or only 1 measurement at screen bottom)
or - make sure System -> Startup is set to 'Last', then select the measurements you want at screen bottom and reboot.

Though maybe not a bug, I noted that when I download a waveform onto a USB drive, the resolution is reduced below that displayed on the scope.  For example, at 2 V/div, the resolution in the downloaded file is 0.080V.  For a full screen deflection of 16V (= 8 x 2V/div ), the # of steps is 200  ( =16V / 0.080V).  I'll have to explore more to see if it is possible to download at higher resolutions.

I'm not sure exactly what you mean? What file format are you talking about? WFM? CSV? TRC?

[marmad]

Those Rigols are feature rich, they have good hardware, but because of those bugs
  I would never trust this scope.    Anyway, when they finally make a good firmware without bugs, it will be a good scope.

I'm not sure what benefit you think these kinds of comments are bringing to this thread, but in any case you're wrong. There are very few bugs in the FW (and certainly nothing serious) - it's completely trustworthy - haven't you noticed that Dave uses it all the time in his videos? And the DS2000 is unquestionably both a more powerful DSO, and a much better deal, than the Agilent DSOX2000.

[Harvs]

I hope to use the decoding functions for our CAN bus, and I am pleased to see some great demos of this capability already posted.

How do you plan on doing that?  As far as I know the CAN bus decoder is only available for the DS6000 scopes (and costs almost as much as a DS2072!)

[devitrify]

I hope to use the decoding functions for our CAN bus, and I am pleased to see some great demos of this capability already posted.

How do you plan on doing that?  As far as I know the CAN bus decoder is only available for the DS6000 scopes (and costs almost as much as a DS2072!)

Harvs, thanks for bringing to my attention my error regarding the CAN bus decoder.  I've been viewing too many videos on Rigol scopes and didn't connect that the CAN bus decoding wasn't available on the DS2102.  I guess I'll only be able to decode the I2C, which we haven't used on our robots as often.

[devitrify]

This bug was just introduced in the last version of the FW - and has already been fixed in the upcoming version. It is in our bug list on the opening page:

Marmed,
I am happy to hear that the bug where data is duplicated in measurements is recent.  Although I had seen it in your post, I thought it worth mentioning because I encountered it quickly when trying out the scope, and so it was one of my "First Impressions" -- the subject of this thread.  I also thought it was a long standing uncorrected bug, so I'm glad to hear I am wrong on that.

Though maybe not a bug, I noted that when I download a waveform onto a USB drive, the resolution is reduced below that displayed on the scope.  For example, at 2 V/div, the resolution in the downloaded file is 0.080V.  For a full screen deflection of 16V (= 8 x 2V/div ), the # of steps is 200  ( =16V / 0.080V).  I'll have to explore more to see if it is possible to download at higher resolutions.

I'm not sure exactly what you mean? What file format are you talking about? WFM? CSV? TRC?

The file format is CSV.
Here is an excerpt after importing the CSV file into MS Excel and changing the number format from scientific to fixed point for readability:
X   CH1   CH2
Sequence   Volt   Volt
0   2.879   0.720
1   3.039   0.560
2   2.879   0.720
3   3.039   0.560
4   2.960   0.560
5   2.799   0.720
6   2.879   0.640
7   2.799   0.560
8   2.879   0.640
9   2.799   0.480

The waveforms were recorded at 2V/div.  The minimum increment is 0.080V. When I plot this data in excel, I find the resulting data is heavily quantized, when compared to the original data that was displayed on the scope.  I've attached the .BMP and .CSV files for comparison; (change .txt to .csv).  I probably don't have an option for downloading to a file set correctly -- I have only a few hours experience with the scope.

[Pinkus]

deleted - double posting -

[Pinkus]

Maybe Rigol will offer CAN decoding on the DS2000 later?

I don't think so. Probably the main firmware set is the same through all DS 2xxx/4xxx/6xxx series and they just enable/disable features (and changes regarding different hardware). By this the firmware development costs are shared through all scope lines and maintaining is much easier.
As of marketing reasons they need to differentiate the misc. scope lines. The more expensive series will get more features then. If they would just enable all possible features in a DS2xxx series scope (e.g. allow 350 Mhz, allow CAN etc. which would not cost them anything but some time for testing), very few people would buy a DS4xxx or DS6xxx series scope. By this they would loose a lot of money.

So, either 'somebody' find out how to enable this in the firmware (if the full code is there) or we will never see it - Rigol will definately not do this. And ... I am pretty sure Rigol people are reading this forum too, so they will (unfortunately) find a way to prevent this.

[Pinkus]

blank post - trying to start a new page to overcome the problem with the 'crashed / hung up thread'

[Pinkus]

blank post - trying to start a new page to overcome the problem with the 'crashed / hung up thread'

[Pinkus]

OK, I do not know what happend, the page 85 was hanging for a few hours after my last post there. I did nothing special, just writing some text.
I now had the idea to add a few blank postings to move the thread to a new page. It seems this worked and the thread it is back to normal again - just one real entry from me is missing and this one was not important. So, end of page 85 is missing and hanging.

Peter

[Yaksaredabomb]

Still appears broken to me - I can only see posts after the attached when I'm in the reply editor, where the new posts appear below the edit box.
 
In case it helps, right now in normal view I can see through "Reply #1270" (attached).  In edit view I can see though the following post:
 

OK, I do not know what happend, the page 85 was hanging for a few hours after my last post there. I did nothing special, just writing some text.
I now had the idea to add a few blank postings to move the thread to a new page. It seems this worked and the thread it is back to normal again - just one real entry from me is missing and this one was not important. So, end of page 85 is missing and hanging.

Peter

[marmad]

Still appears broken to me - I can only see posts after the attached when I'm in the reply editor, where the new posts appear below the edit box.
 
In case it helps, right now in normal view I can see through "Reply #1270" (attached).  In edit view I can see though the following post:

I just posted about this in the Supporter's Lounge where it might get more immediate attention from Dave/the staff.

[devitrify]

I think page 85 broke when I as posting a response to Marmad.  I had trouble uploading a 1.5MB .BMP file, attached to my response, where the page (#85) would timeout when I posted.  I tried 2 or three times, and succeeded with the post only after I removed my attachment. I then went back to modify the post to re-add the attachment, and that's when page 85 started behaving badly. My post exists, attached to my username devitrify, but it doesn't appear on page 85.

[marmad]

I think page 85 broke when I as posting a response to Marmad.  I had trouble uploading a 1.5MB .BMP file, attached to my response, where the page (#85) would timeout when I posted.  I tried 2 or three times, and succeeded with the post only after I removed my attachment. I then went back to modify the post to re-add the attachment, and that's when page 85 started behaving badly. My post exists, attached to my username devitrify, but it doesn't appear on page 85.

@devitrify: I just read your 'vanished' post (and your original post again). Obviously the Rigol, like all other low-cost DSOs, uses an 8-bit ADC, meaning that you would never get more than 256 discrete levels maximum. The Rigol does another trick (I'm not sure why, but I think partially for speed - and partially because of the 500uV/div setting) in which it only maps 200 (of the 256 possible) to the 400 pixel height of the display (25 levels = 50 pixels = 1 division ), effectively causing ~10% of the possible vertical resolution to fall offscreen, top and bottom. If you want to get as much vertical resolution as possible in your saved waveforms, you should adjust the display so the it overlaps the top and bottom by ~10% (one division).

Edit: If you download my software, RUU, it will display 10 divisions (if you check 'Full ADC') so that you can adjust the vertical scale precisely on the Rigol to match the (almost) maximum resolution (250 out of 256).

Here's an image saved of a full 10-division sine wave:

[marmad]

@devitrify: BTW, one other point worth mentioning (which you may or may not be aware of): the DSO is doing sin(x)/x (or linear) interpolation for the display - constructing new data points within the range of the captured sample points; i.e. filling in-between the 'blanks'.  It does not do this normally when you save the waveform - you only get the actual sample points, not the interpolated points - unless you save the display memory, as opposed to the sample memory.

[tinhead]

The Rigol does another trick (I'm not sure why, but I think partially for speed - and partially because of the 500uV/div setting) in which it only maps 200 (of the 255 possible bits) to the 400 pixel height of the display, effectively causing ~10% of the possible vertical resolution to fall offscreen, top and bottom. If you want to get as much vertical resolution as possible in your saved waveforms, you should adjust the display so the it overlaps the top and bottom by ~10% (one division).

other manufacturers doing this as well, 10.24DIV for full scale, so each DIV represents 25 of 255 values.
Sure, they could use as well 8DIV each 32 of 255 values, but then the waveform would clip at the edge of the
screen, this didn't look good. It have as well something with display resolution vs amount of steps per DIV,
so yes, you right, it does speed up the calculation (display engine).

[devitrify]

@devitrify: I just read your 'vanished' post (and your original post again). Obviously the Rigol, like all other low-cost DSOs, uses an 8-bit ADC, meaning that you would never get more than 256 discrete levels maximum.

Marmad, Rigol claims 12 bits of resolution for the DS2000 series in their posted specs at:  http://www.rigolna.com/products/digital-oscilloscopes/ds2000/
but I understand you to say that these additional 4 bits are interpolated from the actual 8-bit measurement.

I am disappointed. I wish that manufacturers would simply state the resolution of their ADCs and separately indicate the means with which they achieve any additional resolution, much like optical vs digital zoom on cameras.

Marmad, I look forward trying out your RUU software.  I've heard good things about RUU while exploring the info on these Rigol scopes.


Edited:  OK, after posting above, I read the specs at Rigol more carefully...
From the specs:
Sample mode
    High Resolution: 12 Bits of resolution when...
Vertical
    Vertical Resolution: 8bit

I just don't know what "Sample Mode" means, and how it differs from the vertical resolution.

[marmad]

Marmad, Rigol claims 12 bits of resolution for the DS2000 series in their posted specs at:  http://www.rigolna.com/products/digital-oscilloscopes/ds2000/
but I understand you to say that these additional 4 bits are interpolated from the actual 8-bit measurement.

I am disappointed. I wish that manufacturers would simply state the resolution of their ADCs and separately indicate the means with which they achieve any additional resolution, much like optical vs digital zoom on cameras.

As far as I've been able to tell, Rigol has always been quite honest about their specifications (although sometimes you need to dig a little), unlike other brands I can think of. The High-Res mode is a commonly used 'trick' among manufacturers at the moment to 'simulate' 12-bit resolution with sample-averaging (perhaps started in lower-cost models by Agilent and their X-Series). But the DS2000 User Manual clearly states:

High Resolution
This mode uses a kind of ultra-sample technique to average the neighboring points of the sample waveform to reduce the random noise on the input signal and generate much smoother waveforms on the screen. This is generally used when the sample rate of the digital converter is higher than the storage rate of the acquisition memory. Note: “Average” and “High Res” modes use different averaging methods. The former uses “Waveform Average” and the latter uses “Dot Average”.

Again, this is something being done ON sample memory in it's transformation to display memory (and the screen). You won't be able to save this except as the 1400 bytes of display memory.

[marmad]

Some cut & paste info about the technique:

High-resolution mode

The second method of averaging in the digitising oscilloscope that does not require a repetitive signal is high-resolution mode.

These types of oscilloscope provide 8-bit vertical resolution in normal acquisition mode, like most other digitising oscilloscopes. However, high-resolution mode on the oscilloscope offers up to 12 bits of vertical resolution in real-time mode, which reduces noise and increases vertical resolution.

Instead of averaging points from multiple acquisitions in a single time bucket like normal averaging mode, high-resolution mode averages sequential points within the same acquisition together.

In high-resolution mode you cannot directly control the number of averages as you can in averaging mode. Instead, the number of extra bits of vertical resolution is dependent on the time/division setting of the scope.

When operating at slow time base ranges, the oscilloscope serially filters sequential data points and maps the filtered results to the display. Increasing the memory depth of on-screen data increases the number of points averaged together.

High-resolution mode has no effect at fast time/div settings, where the number of on-screen points captured is small. It has a large effect at slow time/div settings, where the number of on-screen points captured is large.
 
How to achieve 12 bits of resolution

For the oscilloscope in high-resolution mode, vertical resolution varies as the time base changes as below (at 1Gsample/s sample rate).

Time base   Bits of resolution
<10ns/div          8
50ns/div            9
200ns/div         10
1µs/div             11
> or =5µs/div   12
 
To get up to 12 bits of resolution in high-resolution mode, the oscilloscope averages together at least 16 consecutive samples.

Therefore, to achieve 12 bits of resolution, we add 16 consecutive samples together, then divide the total by 16. This process is commonly referred to as decimation. This results in 12 bits of useful data. Notice that these are bits of resolution, not accuracy.

The effectiveness of high-resolution mode depends on the characteristics of the dominant noise sources, which come internally from the oscilloscope or from external circuits measured by the oscilloscope.

In other words, you only get more “resolution” in the presence of white noise. You may not be able to get more resolution for averaging noise-free samples.

Most A/D converters used in digitising oscilloscopes are 8-bit converters, with 8-bit differential non-linearity (DNL) and 8-bit integral non-linearity (INL). DNL error is defined as the difference between an actual step width, and the ideal value of 1LSB (least significant bit).

The INL error is described as the deviation, in LSB or percent of full-scale range (FSR), of an actual transfer function from a straight line. High-resolution acquisition on a noisy signal will tend to improve DNL characteristics, but not INL. The scope probes and pre-amplifier in the front-end of the oscilloscope are calibrated to a few per cent of accuracy, so those are the dominant component needed to improve the integral non-linearity accuracy.

[Teneyes]

High Resolution
Again, this is something being done ON sample memory in it's transformation to display memory (and the screen). You won't be able to save this except as the 1400 bytes of display memory.

EDIT: Actually, perhaps I'm wrong about this and the results of the averaging end up in sample memory - I haven't tested saving High-Res mode so I'm not sure. But in any case, it will be as 8-bit data, not 12-bit.

  Average is over frames
I found this video a good explaination of sampling, averaging, and High resolution

[marmad]

  Average is over frames

Normal Average is of waveforms.
High Resolution Average is of sample points.

[marmad]