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Functional comparison of R&S RTB2000, Siglent SDS2000X and Keysight DSOX1000

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RBBVNL9:
@pdenisowski

Thanks, Paul, thanks for the compliments. Just did one more test prompted by your message and I indeed do now see how the horizontal scale can be edited after the measurements are done (your point 1) - will add it to the overview table. The topic of resolution/dynamic range for Bode plots is a complex one. For each new measurement, the instrument may reconsider the appropriate channel gain for the measurement, so it is not only dependent on the resolution of the ADC or other related measures (like averaging) but also the ability to jump to the right channel gain, and the highest available channel gain (and its noise floor). So the dynamic range may be more than 8, 10 or even 16 bit would allow for, but how much, depends on other factors.

Topic of next video is not yet decided but it might well be ... FFT

RBBVNL9:

--- Quote ---Just watched the new episode, I would like to know how they perform when encountering a phase shift beyond +-180°. The Keysight 1102g has this thing where it can't determine if the phase is + or - 180° so you see jumps like this when it crosses either point, could you test for this on the 1204g and the others? thank you!
--- End quote ---

Thanks. I recall that the RTB allows you to set the way it 'jumps' when large phase shifts occur. Time permitting I will do the test you asked for - let me see of I have a nice DUT lying around that makes such shifts.

Anthocyanina:

--- Quote from: RBBVNL9 on June 27, 2022, 07:24:46 pm ---...

Topic of next video is not yet decided but it might well be ... FFT

--- End quote ---

Ooh! perhaps you might want to cover this if you do FFT next(or anyone else might know what's going on in here?). I'm not sure if this is a thing with just my unit, or if it's a thing with the model, or if it's different between the 1102 and 1204 series, but I found that when doing FFT at slower timebases for higher RBW, at certain timebases the FFT would just cut off on the right, and the resolution would show up as higher, and then if you move it to either faster or slower timebases, it would expand again and show lower resolution, all this within the 2GSa/s limit of 20µs/. So i find this very strange that if sampling rate isn't changing, the FFT is still cutting off  :scared:

In the screenshots you can see how going from 18µs/ to 18.4 the FFT resolution seems to increase but it chops off the right side, and then changing from 18.4µs/ to 19.2 it comes back, but the resolution seems to go down again.

RBBVNL9:
On request, I have decided to do the FFT episode as the next one in the series. It's quite an extensive topic to cover, resulting in a mammoth video… But I have provided extensive TOC (so you can jump to what you want to see), and I’m sure there are new insights things to be discovered by everyone, also the most seasoned users of these oscilloscopes! 

Once again, the comparison document is updated (now 54 pages, 267 footnotes, quite some detail….).

Enjoy!
Rudi


2N3055:

--- Quote from: RBBVNL9 on July 13, 2022, 07:05:18 pm ---On request, I have decided to do the FFT episode as the next one in the series. It's quite an extensive topic to cover, resulting in a mammoth video… But I have provided extensive TOC (so you can jump to what you want to see), and I’m sure there are new insights things to be discovered by everyone, also the most seasoned users of these oscilloscopes! 

Once again, the comparison document is updated (now 54 pages, 267 footnotes, quite some detail….).

Enjoy!
Rudi


--- End quote ---

Hello Rudi.

I must say that I didn't have time to watch your quite lengthy video in details..
Quite frankly, I don't really agree with some of methodology, and there are some omissions that I caught by only cursory watching..

Let's just touch on some of those, without particular order.

RBW is resolution bandwidth, not realtime bandwidth. You confused them when talking about R&S.

First, there is no RBW in FFT, really. With FFT we talk about frequency bin size (or bin width, or bin spacing).  RTB doesn't have regular FFT implementation. What they have is kind of simplified version of spectrum mode from it's "bigger" brethren..
It is nor proper spectrum mode, nor propper FFT.  That makes it easier to use because it speaks of RBW (while I don't know if they are really calculating proper spectrum plot with recalculated bins to RBW and amplitude and scalloping loss and frequency leakage corrections in accordance with used FFT window etc..) and other parlance like you are using SA..  I presume R&S did it right ( because they should know how it's done) but I don't understand how it is implemented.

FFT is more basic mathematical transformation than full SA implementation. R&S implementation gets you quicker something on the screen, but if you are doing something where FFT needs to be set exactly in some way, R&S is not good for that.
It depends on usage, I guess.

Fact that FFT in RTB2000 takes over control of the scope is annoying as hell to me, personally.. 

On SDS2000X+, sort peaks (frequency/amplitude) is applied to TABLE view. Peaks markers are always enumerated from left to right in increasing number order.

Noise floor comparisons are valid only if you have exactly same number of data points, time interval bins, averaging and same windowing. Otherwise they will differ..

On SDG2000 (or 6000) you don't need to press amplitude for few seconds to get dBm. If you have it set for 50 Ohm, you simply start typing number 0 and press dBm like you did..

I will look at the video in more detail later.. It is kinda busy these days...

Please don't take this as offense. The topic is quite complicated and it is very involved to create representative presentation.. It is obvious a lot of work is put in it. Minor errors are understandable..

Best
Sinisa

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