Hi,
Probably I'm OT but I wonder if it would be possible to group buy this oscilliscope to have a bigger discount for large quantities.
I think a lot of people here would like to buy one of these...
Any ideas?
Thanks!
Is 10x margin enough for sure
Is 10x margin enough for sure, or only expected to be enough? Does that 10x margin still depend on having an acceptable higher order low-pass filter in the analog front-end of the scope?
So although the Rigol DS2000 series goes up to Rigol DS2302A, in reality the best configuration which can be used and meets 10x margin when using 2 channels at the same time, is the Rigol DS2101A. Is that correct?
You seem to be unwilling (or unable) to grasp the very basics of sampling - even though they have been laid out here time and time again. The Nyquist theorem is just that: a mathematical theorem. It is not real world usage - such as trying to get an accurate image of a waveform you're trying to look at. It doesn't take much imagination to see what kind of image a waveform sampled at fs/2 is going to deliver with linear interpolation:
Your simplistic join the dots scheme...
If you put those triangles through a bandpass filter, so remove all the out of band crud you just created, you'll get back to something similar to the original signal.
...2.5 - 4x oversampling can be enough.
...2.5 - 4x oversampling can be enough.
This only applies to signal reconstruction (ie. display), not to the actual sampling process.
Your simplistic join the dots scheme...
Mine? It's just a stock Nyquist image lifted from the internet showing a sine wave sampled at 2f.
QuoteIf you put those triangles through a bandpass filter, so remove all the out of band crud you just created, you'll get back to something similar to the original signal.
Oh please.. do go on! School me on how DSOs are faithfully reproducing waveforms right up to the Nyquist frequency.
There are plenty of idiotic pictures on the web. You chose to quote this one to illustrate something. Maybe you didn't adequately explain what that something was.
They don't faithfully display right up to Shannon, for reasons many people have explained.
However the practical limitations of not being able to impose a brick wall filter without nasty phase effects don't make linear interpolation, with its consequent massive increase in bandwidth, any more meaningful.
Wow, I really don't have the energy to go through this again. Congratulations, you win!
Wow, I really don't have the energy to go through this again. Congratulations, you win!Does this mean we stop talking about it, and start using our scope ?
Does this mean we stop talking about it, and start using our scope ?
This argument over sampling rates and bandwidth is really quite silly....
You volt-nuts may say the scope only has real 25MHz bandwidth on four channels. If that really bothers you, don't buy it. Or turn on the 20MHz filter. (It'd be really nice if Rigol let users enable the 50 and 70MHz filters too, for the 100MHz scopes. I can hope.)
Apologies if this has been pointed out before...
The resistor jumper configuration for "Hardware Version" is different on DS1054Z compared to DS1104Z.
Oh and Pascal, when do you buy an Rigol scope ??
Oh and Pascal, when do you buy an Rigol scope ??
Now there's an interesting question! Let's look back at the last year...
January 01, 2014, 02:40:30 PM »
I am going to buy a digital oscilloscope, but am doubting between the DS1074Z (4 channels) or the DS2072 (2 channels).
January 01, 2014, 05:38:35 PM »
I am interested in DS2072A but want to wait until the hack is confirmed with new FW and all options enabled, including 300MHz and CAN decoding.
January 02, 2014, 04:20:22 PM »
is the DS2072A hackable to 300 MHz with all options or not?
How long does it typically take to come up with a new hack? =) I need to buy my scope latest next week
January 21, 2014, 09:49:04 AM »
Are there any rumours or confirmations about upcoming DS2000 series with built-in LA?
Will the LA have 8 channels or 16 channels? When is it expected? Details on launch date and model numbers? Pictures?
~~ Purchase decisions got deferred, more questions were asked, the LA option awaited. Then he focused on the MSO1074z (after flirting for a bit with the Siglent SDS2000).
June 30, 2014, 03:56:18 AM »
I am considering to buy a new scope now, and am thinking about MSO1074Z, as it seems to have everything I need. 4 Channels is very handy.
July 11, 2014, 07:57:32 AM »
Anybody with more feedback about the MSO2072A or the MSO1074Z?
If you are doing digital design 2 analog channels are more than enough given that you have 16 digital channels.
So that makes me conclude to go for the MSO2072A. Now just need more feedback on it
August 04, 2014, 09:21:00 AM »
Myself am going to order very soon an MSO1074Z, or an MSO2072A. Still doubting about which one is the best, but most likely it will be the MSO1074Z, as 100 MHz (after possible upgrade) would be enough for my current applications. But I really want confirmation that feature wise both scopes are as good.
August 07, 2014, 12:33:46 PM »
From that perspective I think I have finally made up my mind. It is simply going to be a MSO2072A
~~ Finally! But not so fast...
August 09, 2014, 04:49:16 PM »
It actually seems that intensity grading is better on 1074Z series than on 2000A series.
Also the screen contrast is better on the cheaper 1074Z series.
Now I am really confused. Although the screen is smaller on the 1074Z series, the screen quality is better than the 2000A series.
Honestly I am clueless again, and still can not decide then on MSO1074Z or MSO2072A, after seeing this video =)
~~ Marmad finally inquired, 2 months ago: "seriously, man, you've been posting these same questions for over 7 months now... perhaps it's time to bite the bullet and buy a DSO?"
August 13, 2014, 05:43:40 AM »
Yes, I agree. I will buy the scope in September =) [MSO2000, after debating viewing angles vs. 1000z]
~~ But hold on a minute...
September 10, 2014, 05:21:47 AM »
Considering to buy MSO1074Z or MSO2072A. Most likely I will go for MSO2072A.
October 09, 2014, 10:51:54 AM »
I haven't bought the scope yet, as I was waiting on some videos for the LA functionality in the MSO series. But scope will be ordered soon (other priorities now).
~~
My personal suspicion is he won't ever order any DSO. Because: a) he wants it to be perfect, and the "best" in every possible way, b) he wants it to be trivially easy to hack, c) he wants guarantees that it will have no limitations that he might some day run into, and the major #1 reason... (drum roll please)
d) he really has no need for a DSO!
Good summary! Yes, keeps everybody busy!
I will come with the big announcement at the right time
Now I am confused. Are you referring to the analog antialiasing filter before the digitizer or the reconstruction filter after the digitizer? If aliasing occurs then the later cannot do anything about it.
Both are low-pass filters. Leakage is a phenomenon that is not associated with aliasing (since it happens below Nyquist) and is not preventable by antialiasing or reconstruction filters.
Yes, and we established that in the screenshots I made there were no frequency components above Nyquist, so aliasing was not occurring.
note: what results is not really an AM signal, but a DSB signal (or AM with suppressed carrier, the sine does not ride the wave) -equivalent to the summation of the original "real" 120 MHz and the leaked "mirror" at 130 MHz. In the FFT's a few pages ago and attached here you can see that the amplitude of the mirror grows as the sampled frequency approaches Fnyquist. The result is shown as a double-sideband signal, not really an AM signal as there is no power in the central frequency of 125 MHz.
All this is after the digitizer and no aliasing occurring.
So as Marmad noticed this leakage is no issue till say Fsample/2.5 (my 100 MHz). There the leakage is so small is does not show any more.
As I understand it (now) up until Fnyquist you can reconstruct the frequency, but the amplitude information gets lost above Fsample/2.5. Just too few samples, and these samples "shift" along the wave resulting in the AM like waveform
Looking at the samples near Fnyquist themselves I am not even sure that a reliable reconstruction of the amplitude is even possible, and that it has nothing to do with errors in the reconstruction algorithms used by Rigol? At least that is what the documentation Marmad supplied is suggesting.
Interesting learning experience. This goes to show that one should be really really careful when interpreting displayed waveforms even long before FNyquist. So the DS1000Z's are 100 MHz scopes? Yes, but beware..
This post covers the same problem and mentions the Agilent MSO6034 manual which includes a statement about their reconstruction filter having a bandwidth of half the Nyquist frequency:
The leakage is still there. If you look really carefully at the lower frequency examples, you can see the amplitude still varying but it happens at a higher frequency because the signal and image are further apart.
If the filter was long enough, then the 130 MHz image would have been removed. The filter however is shorter than this because of both performance reasons and because the filter length subtracts from the usable record length at the ends where a full set of samples is not available to calculate it.
This post covers the same problem and mentions the Agilent MSO6034 manual which includes a statement about their reconstruction filter having a bandwidth of half the Nyquist frequency:
No, this doesn't cover the same problem; this is you attempting to connect this with a problem the DS1000E had - just as you tried to do before earlier in this thread. Rf-loop and jahonen were discussing the problem of the sin(x)/x interpolation on the DS1000E not matching the actual sample points. That is not the issue at all here - the interpolation matches the sample points just fine (see images).
QuoteThe leakage is still there. If you look really carefully at the lower frequency examples, you can see the amplitude still varying but it happens at a higher frequency because the signal and image are further apart.
Huh? No it doesn't. I just examined his 100MHz image in Photoshop and the amplitude only varies +/- 1 pixel - certainly within the DSO's margin of error, especially since the display memory is 2x scaled from the intensity buffer .
QuoteIf the filter was long enough, then the 130 MHz image would have been removed. The filter however is shorter than this because of both performance reasons and because the filter length subtracts from the usable record length at the ends where a full set of samples is not available to calculate it.
By long enough, do you mean infinitely or impossibly longer? If not, please produce a SINGLE real-world example of a DSO sampling a frequency between fs/2.1 and fs/2.05 and reconstructing the waveform correctly. I would love to see it.
At a lower frequency yet it will become indistinguishable from noise. Pick the right higher frequency and it will be +/- 2 pixels. Pick a higher one yet and it will be +/- 3 pixels.
I cannot give an example of a DSO doing this for the reasons discussed above but textbooks give graphic examples of ideal sin(x)/x reconstruction all the time when they discuss representing all input frequencies up to but not including the Nyquist frequency. How else could a sampled data stream represent all frequencies up to but not included the Nyquist frequency accurately otherwise?
This is the same screenshot of the 120 MHz signal where I counted wrong and you made the same counting mistake:
https://www.eevblog.com/forum/testgear/new-rigol-ds1054z-oscilloscope/msg532229/#msg532229
The signal is a 120 MHz sine wave. The image above the 125 MHz Nyquist frequency is at 130 MHz. After reconstruction with a low pass filter, any remaining part of the 130 MHz image should result in constructive and destructive interference with a beat frequency of 10 MHz which is what the blue line I have added shows.