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

[Wim13]

This input stage is a Hantek / TEKWAY ...

As you can see there are slight differences.

The Rigol has a differnt chip on the entry, that can be programmed for the bandwidth, and can
be changed by software, so very different from the Hantek

From the TI datsheet of this chip:

The LMH6518 gain is programmed via a SPI-1
compatible serial bus. A signal path combined gain
resolution of 8.5 mdB can be achieved when the
LMH6518's gain and the Gsps ADC's FS input are
both manipulated. Inputs and outputs are DC-
coupled. The outputs are differential with individual
Common Mode (CM) voltage control (for Main and
Auxiliary outputs) and have a selectable bandwidth
limiting circuitry (common to both Main and Auxiliary)
• Oscilloscope Programmable Gain Amplifier
of 20, 100, 200, 350, 650, 750 MHz or full bandwidth.


for the 2072 it is 100 Mhz
for the 2102 it is 200 Mhz
for the 2202 it is 350 Mhz

Because of its 1 MOhm entry is loses some of its real bandwidth.
And that is why you see on all models the 20 Mhz filter.

[Carrington]

This input stage is a Hantek / TEKWAY ...

As you can see there are slight differences.

The Rigol has a differnt chip on the entry, that can be programmed for the bandwidth, and can
be changed by software, so very different from the Hantek

From the TI datsheet of this chip:

The LMH6518 gain is programmed via a SPI-1
compatible serial bus. A signal path combined gain
resolution of 8.5 mdB can be achieved when the
LMH6518's gain and the Gsps ADC's FS input are
both manipulated. Inputs and outputs are DC-
coupled. The outputs are differential with individual
Common Mode (CM) voltage control (for Main and
Auxiliary outputs) and have a selectable bandwidth
limiting circuitry (common to both Main and Auxiliary)
• Oscilloscope Programmable Gain Amplifier
of 20, 100, 200, 350, 650, 750 MHz or full bandwidth.

Yes, but something makes me think that there is something more.
Imagine sending the command to 750MHz BW 

As you can see there are more things besides the LMH6518.

I wonder how the input stage seems to the schematic at the LMH6518 datasheet...

It is likely that there are differences in the input stages of the DS2000 series.

[marmad]

sorry I may be late to the party..

The anti-aliasing function may not do what you expect but it does work. Here is an example same signal with and without anti-aliasing.  I should have tried to zoom in to see what the actual waveforms look like. But there is some difference
CH1 is ~700Hz and CH2 is @ 7 MHz envelopes.   The second picture - Antialiasing ON

This has nothing to do with what I expect - it has to do with what anti-aliasing MEANS in terms of DSOs. What you are showing in your images has nothing to do with anti-aliasing in reference to a DSO. If you think it does, give me a link to an explanation (which contains the terms 'anti-aliasing' and 'DSO'). OTOH, I can you dozens of links to explanations of what anti-aliasing SHOULD be doing on a DSO.

I know the Rigol is doing SOMETHING when you turn on anti-aliasing, but it's definitely NOT doing anti-aliasing as defined for DSOs - thus it DOES NOT WORK.

[marmad]

It is likely that there are differences in the input stages of the DS2000 series.

Wim's chart of the different BW's of the different models was all made on the same DSO - he just changed the BW via software codes.

[Carrington]

It is likely that there are differences in the input stages of the DS2000 series.

Wim's chart of the different BW's of the different models was all made on the same DSO - he just changed the BW via software codes.

Oh I understand, sorry for the confusion. 

Imagine sending the command to 750MHz BW 

[zibadun]

I know the Rigol is doing SOMETHING when you turn on anti-aliasing, but it's definitely NOT doing anti-aliasing as defined for DSOs - thus it DOES NOT WORK.

I think this function changes how captured samples are mapped to pixels on the screen to minimize aliasing.  It doesn't change the way the signal is sampled. It works when scan rate is much slower than the sampling rate.  What did you expect this button to do?

[Carrington]

Imagine sending the command to 750MHz BW 

I understand that a member, tried setting higher BW modes with the Hardware hack and the the DS2000 is NOT capable of more BW

Any idea of why this happens. 
Get at least at 400MHz/350MHz would be very good (at 50ohm).

[Chet T16]

My DS2072 has arrived Can't even open the box until my wife gets home

[Carrington]

Another curious thing, look at the pictures.
Where is the difference?

[Wim13]

My DS2072 has arrived Can't even open the box until my wife gets home

What has your wife to do with it.., did she gave it as a present...

[Wim13]

Another curious thing, look at the pictures.
Where is the difference?

i dont get it, please more ext

[marmad]

I think this function changes how captured samples are mapped to pixels on the screen to minimize aliasing.  It doesn't change the way the signal is sampled. It works when scan rate is much slower than the sampling rate.  What did you expect this button to do?

Anti-aliasing never changes how the waveform is sampled. But you seem to be thinking about IMAGE anti-aliasing - I'm speaking about WAVEFORM anti-aliasing; which is what a DSO is supposed to do if it has an anti-aliasing feature (it has nothing to do with jagged edges, pixels, etc).

This post and the following one provide more information.

[Carrington]

Another curious thing, look at the pictures.
Where is the difference?

i dont get it, please more ext

IMHO, the BW is lower in the DS2202, but little more I can say. 
I have a SDS8102V (real BW ~206MHz), when I have a DS2072 I will do more comparisons (DS2072 as DS2202).
What do you think?

[Wim13]

Another curious thing, look at the pictures.
Where is the difference?

i dont get it, please more ext

IMHO, the BW is lower in the DS2202, but little more I can say. 
I have a SDS8102V (real BW ~206MHz), when I have a DS2072 I will do more comparisons (DS2072 as DS2202).
What do you think?

I can not see on Agilent what the settings are...to compare

But what is lower then the 2202, to your opinion ?

See picture with a rise time of 1.5 nSec that is 350/1.5  is 233 Mhz,
what is also measured with a signal generator

[Carrington]

Another curious thing, look at the pictures.
Where is the difference?

i dont get it, please more ext

IMHO, the BW is lower in the DS2202, but little more I can say. 
I have a SDS8102V (real BW ~206MHz), when I have a DS2072 I will do more comparisons (DS2072 as DS2202).
What do you think?

I can not see on Agilent what the settings are...to compare

But what is lower then the 2202, to your opinion ?

See picture with a rise time of 1.5 nSec that is 350/1.5  is 233 Mhz,
what is also measured with a signal generator

The ridges (In the images above), should have higher frequency components that 233MHz.
It seems that these only be seen with more than 300MHz of BW.

My SDS8102V have a similar BW and I can make a better comparison. 

[Carrington]

Another curious thing, look at the pictures.
Where is the difference?

Yes , I see a picture of 500Mhz Agilent Scope
with a Label of OWON , what is your point??
You like bullshit!!

Oh no please do not misunderstand me. Respect please. I'm just saying what I think. Owon is not the best, but recognize that in the image above is nothing short, regarding BW.
Please understand that my native language is not English, so may that I am not express properly.

[EV]

See picture with a rise time of 1.5 nSec that is 350/1.5  is 233 Mhz,
what is also measured with a signal generator

It is even better. Look at the picture, there rise time is 1.32 ns which gives BW = 350 / 1.32 = 265 MHz.

[Carrington]

See picture with a rise time of 1.5 nSec that is 350/1.5  is 233 Mhz,
what is also measured with a signal generator

It is even better. Look at the picture, there rise time is 1.32 ns which gives BW = 350 / 1.32 = 265 MHz.

Imagine doing the test (rise time) using this:
http://www.maxim-ic.com/an3699
The result probably be closer to the oscilloscope real BW.

Thanks EV.

[zibadun]

I think this function changes how captured samples are mapped to pixels on the screen to minimize aliasing.  It doesn't change the way the signal is sampled. It works when scan rate is much slower than the sampling rate.  What did you expect this button to do?

Anti-aliasing never changes how the waveform is sampled. But you seem to be thinking about IMAGE anti-aliasing - I'm speaking about WAVEFORM anti-aliasing; which is what a DSO is supposed to do if it has an anti-aliasing feature (it has nothing to do with jagged edges, pixels, etc).

This post and the following one provide more information.

 Marmad, I understand what aliasing is.  I don't believe it's a bug or even annoyance if this option does not let you to measure a 1 MHz signal with 200 kSa/s

You need to use a high enough sampling rate for the signal being measured and also make sure that any higher frequency components are cut off with a low pass filter.  There is no way around it.   

May be you are thinking of undersampling when you are actually interested in displaying aliased frequencies.  But this mode still requires proper analog filtering to work correctly..  I bet one cycle of free trial options that  IMAGE anti-aliasing is what Rigol had in mind and it's working as designed.  

[marmad]

Marmad, I understand what aliasing is.  I don't believe it's a bug or even annoyance if this option does not let you to measure a 1 MHz signal with 200 kSa/s

zibadun: Man, we've been talking about this for ages already here - it's not about measurement; it's about incorrect display. The point is - you shouldn't see a waveform of a lower frequency - you should see (what looks like) noise (see what the 1MHz waveform SHOULD look like at that time base).

And, BTW, it's not just about 1MHz @ 200kSa/s - it's ANY frequency at a slightly lower sample rate - it doesn't work at any level.

You need to use a high enough sampling rate for the signal being measured and also make sure that any higher frequency components are cut off with a low pass filter.  There is no way around it.

Of course there is - Agilent does it. It's actually fairly easy - there are papers written about it (linked in earlier posts in this thread). You just do random decimation from sampled data to display data (e.g. instead of displaying every Nth sample, you vary the decimation). So instead of seeing a FALSE lower frequency, you see NOISE.

I bet one cycle of free trial options that  IMAGE anti-aliasing is what Rigol had in mind and it's working as designed.

No - that's not what they had in mind - look at the manual excerpts. It's perhaps what the guy who coded it had in mind, but he FUCKED UP! It's a bug, mistake, or unimplemented feature - there is no way around that fact.

[Carrington]

Oh no please do not misunderstand me. Respect please. I'm just saying what I think. Owon is not the best, but recognize that in the image above is nothing short, regarding BW.
Please understand that my native language is not English, so may that I am not express properly.

@ Carrington
Yes sorry , and I apologize

 To be complete you could say you are comparing :

 A  Rigol     DS2072(hacked)   with 2.0 GSa/s  at  $800  200 Mhz
 A  Owon      SDS9302          with 3.2 Gsa/s  at $1500  300 Mhz
 An Agilent   DSO-X-3502A      with 4.0 GSa/s  at $8000  500 MHz

In fact, I took it for granted. Thank for your clarification. 

[zibadun]

zibadun: Man, we've been talking about this for ages already here - it's not about measurement; it's about incorrect display. The point is - you shouldn't see a waveform of a lower frequency - you should see noise (see what the 1MHz waveform SHOULD look like at that time base).

...

Of course there is - Agilent does it. It's actually fairly easy - there are papers written about it (linked in earlier posts in this thread). You just do random decimation from sampled data to display data (e.g. instead of displaying every Nth sample, you vary the decimation). So instead of seeing a FALSE lower frequency, you see NOISE.

I saw the "random decimation" note.   You can  prevent aliasing from appearing on the lower resolution image but you can't remove aliases from the sampled waveform if you selected too low sampling rate for your signal. There is simply no data about what was happening in between the samples.  You can't look back and apply some algorithm that will turn aliases into noise and will leave "real" frequencies untouched. 

Here is what I can get this function to do.  Note false paterns removed by  the Antialiasing feature.    Sometimes it has the opposite effect and makes the picture worse. You just have to toggle on and off and use the one that looks better.   Now show me the Agilent 1 Mhz sampled with 200 khz rate and turning it into noise

[marmad]

I saw the "random decimation" note.   You can  prevent aliasing from appearing on the lower resolution image but you can't remove aliases from the sampled waveform if you selected too low sampling rate for your signal. There is simply no data about what was happening in between the samples.  You can't look back and apply some algorithm that will turn aliases into noise and will leave "real" frequencies untouched.

I can't believe you're still arguing this point. Anti-aliasing is a proven mathematical formula which works (if implemented correctly). Random decimation is equivalent to stochastic sampling:

"By sampling stochastically, there is no "Nyquist frequency" to talk about, so aliasing will no longer be a problem as before. However, this comes at a price. What you gain in anti-aliasing, you lose by noise in the system. The stochastic sampling introduces high-frequency noise, although for several applications (especially in imaging), aliasing is a much stronger nuisance than noise."

How well does it work? Well, the Agilent X-Series DSOs have anti-aliasing on ALL THE TIME - you can't even turn it off. Now I personally think you should have the ability to switch it off, since it can generate 'lumpy' looking waveforms when zooming in on slightly under-sampled waveforms (caused by the above-mentioned introduction of noise) - but the point is that it works to prevent aliasing. There is no question that it works - but Rigol HAVE NOT IMPLEMENTED IT CORRECTLY!

Here is what I can get this function to do.  Note false paterns removed by  the Antialiasing feature.    Sometimes it has the opposite effect and makes the picture worse. You just have to toggle on and off and use the one that looks better.

Sorry, this is not correctly implemented anti-aliasing. If you think it is, you don't understand the process.

[Teneyes]

Here is an effect of the signal input frequency passing through some sort of beating snyc with the a sample rate of at only 4 times the input
The DSO is Sampling at 2MSa/s
Anti-Aliasing ON

Note the input varies from 499.900 KHz to 500.002 KHz  SAwtooth Waveform
note the Frequency Counter in top Right

I find it interesting, and I will watch for it, as an error
I think this shows a fixed sample collection frequency and not a Random one

An excerpt from Agilent
---------------------------------------------------
Random decimation (see References)
Simple decimation (= regular sampling) is the most common decimation technique in
DSO’s and it is exceptionally prone to aliasing. However, the discarded samples can be
used to prevent the display of aliased waveform. The random sample selection prevents
an alias (or beat) frequency from developing by converting low frequency “spurs” to noise.
(For masochists only ? A. V. Balakrishnan: On the Problem of Time Jitter in Sampling,
IRE Trans. on Info. Theory, April 1962.)
With random decimation (= stochastic sampling) the resulting display is a fuzzy band much
like what would be seen on an analog scope.

However, this technique should be turned off for analysis that requires samples at exact regular time intervals.

Edit  UPDATE
  Setting Memory Depth to Auto in Last picture, all Good

[g2]

Hello
There is  a new firmware to Rigol DS2000:
DS2000(DSP)update_00.01.01.00.02.