Products > Test Equipment
Functional comparison of R&S RTB2000, Siglent SDS2000X and Keysight DSOX1000
rf-loop:
--- Quote from: RBBVNL9 on April 04, 2022, 07:32:01 pm ---Preparing for a new video on observing infrequent events and mask tests, and seeing huge differences there, so I thought I should first dig a bit more into actual triggering behaviour.
I see something I am not sure I understand well.
In short:
- I feed all oscilloscopes with a 1kHz square wave on channel 1.
- I set the horizontal time base such that I see two periods on the screen (200uS/DIV on the SDS and DSOX, and 170uS/DIV on the RTB as it has 12 instead of 10 horizontal divisions). Attaching a pic.
- I activate the trigger out on each device and look at these on a fourth oscilloscope (a PicoScope 3405D). Channels are 1: RTB, 2: SDS, 3: DSOX and 4: input square to scopes.
All scopes are set to regular trigger settings (trigger on positive edge, level halfway square, no holdoff, DC coupling, no noise reject or filter). Record length / memory depth is chosen for best results, if there is any difference. Segmented acquisition off. Auto trigger or normal trigger makes no difference on any of the devices. Lastly, on the RTB I set the trigger out a pulse to 1mS to make it well visible (using SCPI command TRIGger:OUT:PLENgth 1E-3).
Ideally, I would expect to see a trigger every one out of three periods (where the positive edges of the two other periods are shown on the screen), so a constant 333.3 pulses per second on the trigger out bus. After all, 1kHz is such a slow signal and any eventual blank time these scopes need to write to memory etc. should be neglectable.
The results are in the attached screen print.
- The Keysight DSOX behaves exactly as expected, triggering every third period.
- The Rohde & Schwarz RTB mostly every third period but there are some (predictable) interruptions. Is the scope doing something else every once in a while ?!?
- The Siglent SDS triggers much, much less. Only 30 pulses per second instead of the expected 333.
Can anyone enlighten me? Why does the RTB have periodic interruptions? And, more importantly, why is the SDS so slow to re-trigger ?!?
Do I overlook relevant device settings?
Thanks for your insights!
--- End quote ---
Please can you clarify every oscilloscope sampling speed and current acquisition true memory length used in this image.
dreamcat4:
ah ok. but then does that lecroy 3000 series actually have the feature in question? if it is actually a rebranded siglent and not a true windows based lecroy scope?
the feature seems to be able to detect any arbitrary random glitches or anomalies. such as the failed or unclean logic transitions etc
2N3055:
--- Quote from: Someone on April 05, 2022, 07:53:21 am ---
First I think dot mode is not a normal situation to use a scope when wanting to look at waveforms! Its these sorts of "games" that can make comparisons silly, always best to try and find a common setting that all products can meet (and mention that they can do better in their special/preferred setting).
A problem with blind time as a measure is that it is not a constant/deterministic value in most (all?) scopes when in realtime mode, it may be accurate for sequence/segmented modes where nothing is drawn to the screen.
--- End quote ---
I agree with you in general. But fact is that SDS6000H12 works well in dot mode. As soon as you have 1000 pixels horizontally, it looks like continuous line, without any interpolation artefacts. Retriggered events overlay on top and you get SARI, a RIS alike random repetitive sampling. So I keep jumping between line and dot mode.
But making clear specifications is important. It's a shame not even big ones are doing it right. There is a Keysight whitepaper where they compare 3000T wfms/s with competition, carefully choosing test to favour Keysight. And forgetting to mention that much more expensive Keysight scopes have like 100 Wfms/s trigger rate because they have large memories and are doing full buffer managements on large datasets.
They also mention casually memory sizes, but 3000T has only 500k of sample memory when doing 4ch+ digital normal mode (4 buffer-2 per ch-1 with digital -0.5 Mpts for ping pong buffers. 1Mpts for Single mode). Scope with 100Mpts will be 100x slower everything else being equal. Scope with 500MPts will have soo much more work to do.
To make it short, Keysight will have faster retrigger rate because it is specifically designed to do so. Siglent was made to work LeCroy way, and those don't maximize raw retrigger rate but analytic capabilities in long memory.
2N3055:
--- Quote from: dreamcat4 on April 05, 2022, 08:30:03 am ---ah ok. but then does that lecroy 3000 series actually have the feature in question? if it is actually a rebranded siglent and not a true windows based lecroy scope?
the feature seems to be able to detect any arbitrary random glitches or anomalies. such as the failed or unclean logic transitions etc
--- End quote ---
Not even windows based Wavesurfers have that feature fully implemented (parametric triggers).
But you have advanced triggers on Siglent Touch series and also always running (if enabled) search function that you can parametrize to look for several waveform parameters. Those can detect runts, non monotonic edges, slow edges, pulse widths out of spec etc... Combined with advanced triggers it has (including zone triggers), measurements and history mode there are many things that can be detected.
2N3055:
--- Quote from: RBBVNL9 on April 05, 2022, 08:16:59 am ---Thanks all for digging so deep into this. And thanks to 2N3055 for suggesting clear terminology. I noted that sometimes specifications sheets are also not super clear on this. The SDS2000X+ spec sheets talk both of “waveform capture rate” and “waveform update rate”. They seem to mean the same thing with these two terms, but I’m not 100% sure and find it confusing. .....
--- End quote ---
Just to make it clear, it wasn't a critique to you, but a suggestion to actually address that problem you're mentioning: a nonuniform language that confuses us all. If we agree to common language, we understand each other better..
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version