| Products > Test Equipment |
| REVIEW - Rigol DS2072 - First Impressions of the DS2000 series from Rigol |
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| marmad:
--- Quote from: evanh on November 19, 2013, 01:38:24 pm ---High-res acquisition mode operates in oversampling only --- End quote --- No, it CAN use oversampling - but it's not a prerequisite. Just look at the specs for the Agilent 2000 X-Series High Res mode at the following time base settings: 2us = normal sample rate 2GSa/s (no oversampling) = 9 bits of high res 5us = normal sample rate 2GSa/s (no oversampling) = 10 bits of high res 10us = normal sample rate 2GSa/s (no oversampling) = 11 bits of high res Successive sample averaging ("High Res") is purely a math operation on either incoming or stored samples - oversampling can be used, but it's not a necessity. --- Quote ---Rigol doesn't do this, so, although it is high-res, it's not an acquisition mode. --- End quote --- Oh, so now you're admitting that the Rigol IS doing successive sample averaging? Just that it's not an "acquisition mode"? ;D |
| Carrington:
--- Quote from: marmad on November 19, 2013, 11:26:52 am --- --- Quote from: Galaxyrise on November 17, 2013, 07:50:13 am ---See that the sample rate is 1Gsa/s in my screenshot, which should leave plenty of effective sample rate for a 100kHz signal. --- End quote --- @Galaxyrise: Interestingly, the reason the 100kHz signal is so attenuated in the image you posted is that it falls almost directly in the first null point of the stopband @ 1ms/div (see image above which shows the null points of an averaging filter). Compare it to this image using the same settings as you, but with a 150kHz sine wave - which falls beyond the first null point (although still attenuated by -12dB): Playing around with sending sweeps to the Rigol while in High Res mode reveal the nulls that exist in the stopband at each time base setting (while using 14MB/AUTO mem depth). These null points are at the averaging frequency (sample rate/number of samples averaged) and its harmonics. Bandwidths @ different time base settings in High Res mode on DS2000 Time base Bandwidth (-3db) First null in stopband 10ms/div~4.3kHz~10kHz5ms/div~8.6kHz~20kHz2ms/div~21.6kHz~50kHz1ms/div~43.3kHz~100kHz500us/div~86.6kHz~200kHz200us/div~173.2kHz~400kHz100us/div~346.4kHz~800kHz50us/div~692.8kHz~1.6MHz20us/div~1.38MHz~3.2MHz10us/div~2.77MHz~6.4MHz5us/div~5.54MHz~12.8MHz --- End quote --- By limiting the BW seems to be designed for audio applications, or something like that. For now I never used this mode. I am more interested in the ANTI-ALIASING option, I would like to know how RIGOL implemented it, what sampling method used etc... |
| Mark_O:
--- Quote from: marmad on November 19, 2013, 11:26:52 am --- Bandwidths @ different time base settings in High Res mode on DS2000 Time base Bandwidth (-3db) First null in stopband 10ms/div~4.3kHz~10kHz5ms/div~8.6kHz~20kHz2ms/div~21.6kHz~50kHz1ms/div~43.3kHz~100kHz500us/div~86.6kHz~200kHz200us/div~173.2kHz~400kHz100us/div~346.4kHz~800kHz50us/div~692.8kHz~1.6MHz20us/div~1.38MHz~3.2MHz10us/div~2.77MHz~6.4MHz5us/div~5.54MHz~12.8MHz --- End quote --- Thanks for this table, BTW. That's very useful info to have, and not provided by any of the vendors, to my knowledge. |
| marmad:
--- Quote from: Mark_O on November 19, 2013, 03:25:12 pm ---Thanks for this table, BTW. That's very useful info to have, and not provided by any of the vendors, to my knowledge. --- End quote --- No problem - although I went back and edited the title of the table to: Bandwidths @ 14MB/AUTO memory depth in High Res mode on DS2000 ...because the DSO will use lower sample speeds (and thus lower bandwidths) if you don't have the memory depth set to 14MB or AUTO (and possibly 56MB, although I didn't test that). |
| Galaxyrise:
--- Quote from: Carrington on November 19, 2013, 02:24:31 pm ---By limiting the BW seems to be designed for audio applications, or something like that. For now I never used this mode. I am more interested in the ANTI-ALIASING option, I would like to know how RIGOL implemented it, what sampling method used etc... --- End quote --- Anti-aliasing is also done sample->display time, and it's almost useless since the "normal" sample->display decimation algorithm rarely introduces aliasing. And in high res, it actually tends to make aliasing worse! What most people expect anti-aliasing to do, ie minimize sample-rate induced aliasing, Rigol's anti-aliasing cannot do. It can make the display a little nicer looking sometimes, but I think it's generally a waste of update rate. There have been quite a few posts in this thread about it, if you have an afternoon to kill ;) |
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