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Products => Test Equipment => Topic started by: rowifi on May 27, 2019, 01:44:58 pm

Title: Will the Rigol MSO5000 do THIS ..
Post by: rowifi on May 27, 2019, 01:44:58 pm
I've a specific application that needs segmented memory.
I need to capture EVERY half wave of a mains cycle ( 50Hz ) over say a 5 second period.
I accept there will be a short time where the scope needs to re-trigger ( say on the 50Hz zero cross point ), which means I won't get ALL the waveform, but hopefully most of it. A re-trigger 'dead time' of less than 500uS would just be acceptable but the faster it can do it the better.
I understand that some scopes operating in this mode do not update the display while doing the capture - this is acceptable.
I need the capture to analyse it with at least 1uS or better resolution.
This implies a single half cycle using 10,000  (10K )memory points. One seconds worth of data ( 100 half cycles ) is 100x10,000 points ( 1M pt)
Having all the captured segments in memory for 5 seconds is 5Mpt. Clearly with 20M or more I can store at much higher resolution.

Is it possible to replay this data on the screen and overlay each segment one by one to compare them against each other?
Is this scope capable of retriggering this fast without too much loss of data between triggers - if so what is the best retrigger delay attainable in this case.

FYI. The R&S RTB2000 series can do this - but the overlay ( multiple persistence if you like ) does not work properly.

I tried it on a Rigol DS7000 but couldn't get it to do it properly - possibly a very early FW version.
Anyone having a MSO5000 could comment on this.

Title: Re: Will the Rigol MSO5000 do THIS ..
Post by: timber23 on May 27, 2019, 03:40:22 pm
I'm not quite sure, how your measurement should look like.

I did the following test for you. 10 seconds measurement of 230V mains with 2MSa/s. I took this measurement with single shot and stored it to RefA. After that I took another maesurement and stored it to RefB. Finally I did a "math" substraction RefA-RefB. The result is attached.

Is this of any help for you?
Title: Re: Will the Rigol MSO5000 do THIS ..
Post by: 2N3055 on May 27, 2019, 04:48:51 pm
Could you explain what are you trying to accomplish??
Title: Re: Will the Rigol MSO5000 do THIS ..
Post by: PeDre on May 27, 2019, 06:10:13 pm
The Rigol MSO2000A can record 15.4 ms of a cycle at one channel and 14 kSamples, every 20 ms. The 500 recordings cannot be superimposed afterwards. But a mask can be created from a recording and the recordings can be searched automatically with Pass/Fail.
I just tried it quickly, maybe you can improve the settings.
There is also the 'Analysis Based on Trace', but I haven't used it yet.

Peter
Title: Re: Will the Rigol MSO5000 do THIS ..
Post by: timber23 on May 27, 2019, 06:54:21 pm
I tryed the pass/fail test, but I think it is not what you are looking for. After thinking about your request, it seems you are looking for an autocorrelation function. I found this paper: https://link.springer.com/article/10.1134/S0020441219010081 (https://link.springer.com/article/10.1134/S0020441219010081)
They used a RIGOL oscilloscope to do a similar search for annomalies. To accoplish the task, they processed the data with a PC and did the calculation in a self written software. Maybe this is what you want?
Title: Re: Will the Rigol MSO5000 do THIS ..
Post by: thm_w on May 27, 2019, 07:50:43 pm
I tried the pass/fail test, but I think it is not what you are looking for. After thinking about your request, it seems you are looking for an autocorrelation function. I found this paper: https://link.springer.com/article/10.1134/S0020441219010081 (https://link.springer.com/article/10.1134/S0020441219010081)
They used a RIGOL oscilloscope to do a similar search for anomalies. To accomplish the task, they processed the data with a PC and did the calculation in a self written software. Maybe this is what you want?

Yeah sounds like the realistic solution, do a single trigger and record for 5 seconds, transfer the data to a PC, then do whatever analysis in matlab/etc.
Then that opens you up to tons of more correlation/math operations that are not available the oscilloscope.

Quote
Is it possible to replay this data on the screen and overlay each segment one by one to compare them against each other?
Compare what exactly?
Overlay all can be done by turning on infinite persistence, but that's probably not what you want to do.
Title: Re: Will the Rigol MSO5000 do THIS ..
Post by: rowifi on May 27, 2019, 08:16:14 pm
I've not yet read  all your posts, but to clarify I'm trying to monitor the cycle by cycle changes of the output of a light dimmer, comparing one cycle (half) to the next. Checking for linearity and any oddities during a fade event.
Title: Re: Will the Rigol MSO5000 do THIS ..
Post by: rowifi on May 27, 2019, 08:23:54 pm
Thanks for all your checking and time.
If the fade is so timed, then there can be a change in the switching time every cycle, depending on the dimmers fade resolution, for slow fades sometimes more than one cycle, but for fast fades then the dimmer will need to 'jump' through steps. Analysing each cycle or step change permits discovery of timing errors etc or fade comparisons between different settings.
Title: Re: Will the Rigol MSO5000 do THIS ..
Post by: rowifi on May 27, 2019, 08:39:06 pm
Attached image from RTB2004, showing several frames (segments) overlaid, note that the separation between each edge is not equal, this is due to missed captures an a bug in the R&S overlay history function. The reason I'm checking the 5000 can do this is because of this bug.
What im doing is clarified here... but showing the replay problem.
https://youtu.be/S_kzyl3Fygc
Title: Re: Will the Rigol MSO5000 do THIS ..
Post by: nctnico on May 27, 2019, 08:45:31 pm
I have been playing with the segmented replay function on the RTM3004 as well. IIRC you have to select the start segment and then press the 'play' button to get an overlay of multiple segments. Everytime you select a different segment manually, it seems you reset the replay function.
Title: Re: Will the Rigol MSO5000 do THIS ..
Post by: rowifi on May 27, 2019, 08:47:51 pm
I had thought of doing the single trigger capture and analysing the entire capture, but the ability to quickly replay through a few segments and measure the switching times is easier if they are overlaid. I don't want to do any complex math as it's realy just a visual simple timing measurement between dimmer level changes.
Title: Re: Will the Rigol MSO5000 do THIS ..
Post by: rowifi on May 27, 2019, 08:49:57 pm
I don't know about the RTB3000, but the anomalies have been acknowledged as a bug in the 2000 firmware. TBH I don't know the difference between overlay and envelope... they  kind off seem to mean the same.
Title: Re: Will the Rigol MSO5000 do THIS ..
Post by: nctnico on May 27, 2019, 09:20:33 pm
I just did some testing on the R&S RTM3004. With firmware version 1.4 the overlay is buggy but with the latest version (1.5) it works as expected. You can select segments which will then be drawn on the screen as expected.

Overlay and envelope are different. Envelope will show the extremes, overlay will just draw the signals on top of eachother.

BTW a new feature on the RTM3004 is to have tracking math functions. This would mean you can have the duty cycle of a signal as a math trace. It seems the measurement you (rowifi) want to do might even be simpler using tracking math.
Title: Re: Will the Rigol MSO5000 do THIS ..
Post by: rowifi on May 28, 2019, 08:29:54 am
That's interesting. I still don't understand the difference between envelope and overlay. I get that envelope uses a brightness scaling perhaps, but you can select both together.
R&S haven't informed me of a fix for the 2000 .. I don't really want to spend on the 3000 for sure.
I've got over the need now but if the Rigol 5000 can do this very thing correctly, with minimal retrigger time, then it's a much easier spend.