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

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Evi:

--- Quote from: marmad on April 28, 2013, 11:48:36 am ---
--- Quote from: Evi on April 28, 2013, 09:45:10 am ---My result

--- End quote ---
Thanks, Evi!  Are you using USB or LAN connection?

--- End quote ---


I used USB

marmad:
More on memory reads:

The Rigol certainly isn't a speed demon when it comes to large memory-depth reads from the DSO. As mentioned before, they seem to have taken care that transfer routines won't interfere with local operation of the scope (via the front panel). While I understand this philosophy in terms of reading display memory (or sample lengths <= 14k) which you might want to do real-time while the DSO is running, I don't really understand it when you're trying to get large captures out of the scope - which has to be stopped while you're doing it.

For example, to read 56MB out of the DSO takes between ~4.5 - 5.5 minutes via USB (depending how clever you are with timing your requests to the Rigol's buffer being filled - and LAN probably takes longer). Compare that to a 56MB save to USB stick: I just timed it with a stopwatch and it took 5 minutes 23 seconds - so they are more or less equivalent (with external transfer being slightly faster). So we can calculate, roughly, that it takes ~1 minute per 10 megabytes  to save memory either to USB or external device.

So perhaps the bottleneck is not so much of a conscious design decision as it is a limitation imposed by extracting sample data from the pathway that normally runs between acquire memory, display memory, and the LCD.

marmad:
Some sample memory read times in seconds - from the Rigol to the PC using USB (not optimized - and I can't do 7MB or 28MB because of the current two-channel bug). You'll notice <= 14kB is always close to a tenth of a second (although this can be reduced somewhat through optimization). This is slower than reading the display memory - which probably makes sense in terms of internal memory organization:

Reading (AUTO) 70 bytes
Time = 0.0950054

Reading (AUTO) 140 bytes
Time = 0.0890051

Reading 7kB
Time = 0.0950054

Reading 14kB
Time = 0.1010058

Reading 70kB
Time = 0.3350191

Reading 140kB
Time = 0.8340477

Reading 700kB
Time = 2.7551576

Reading 1.4MB
Time = 7.2544149

Reading 14MB
Time = 72.1121246

Reading 56MB
Time = 288.5375034

marmad:
Measuring the Trigger Output delay of the Rigol. Here it is fed back into channel 2, and it appears the delay is ~220ns:

marmad:
Hmm... this Trigger Out delay time used to be something that manufacturers specified in the datasheets (or supplementary literature). But I can see no mention of it in either Rigol's docs - or the literature for the Agilent X-Series or the GW-Instek GDS-2000A materials. Lazy backsliding!  ;)

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