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| REVIEW - Rigol DS2072 - First Impressions of the DS2000 series from Rigol |
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| Xyphro:
Teneyes: i tried the same, but get to see discrete steps (blank lines) on my scope. Which fw version do you use? Mine is listed in the previous posting. Maybe this is a new "feature" of my version? |
| marmad:
--- Quote from: Xyphro on July 07, 2013, 02:19:26 pm ---I'm very confident, that the 500uV mode is a scaled mode and the gain in the analog path is the same as for the 1mV/DIV setting. --- End quote --- So send an email to Rigol and get their response. |
| Wim13:
--- Quote from: Xyphro on July 07, 2013, 02:54:25 pm ---Teneyes: i tried the same, but get to see discrete steps (blank lines) on my scope. Which fw version do you use? Mine is listed in the previous posting. Maybe this is a new "feature" of my version? --- End quote --- I have also a kind of interlaced screen only on 500 uV see pictures below, 500 uV and 1 mV Both had same input on both pictures. on 1 mV the screen is not interlaced. i dont get this picture of Tenyes on 500 uV. stays interlaced on dots. |
| zibadun:
--- Quote from: marmad on July 07, 2013, 02:42:21 pm --- --- Quote from: zibadun on July 07, 2013, 12:52:03 pm ---If RUU is fast enough to render 3d it should be fast enough to draw "anti-alias". You can do it on a stored waveform, as a proof of concept. A picture worth a thousand words in this case ;) --- End quote --- The math data on how to do it is readily available online - and used (at the very least) in the Agilent X-Series. Exactly what am I trying to prove and to whom? ??? --- End quote --- Agilent does this by first estimating the highest frequency component in the measured signal and then selecting a sampling rate which is fast enough to prevent aliasing. The captured samples are displayed using a technique you describe to avoid moire patterns on the screen. Rigol does the same thing more or less. I uploaded an example of this which you simply dismissed ;) If you override scope settings and force 200 ksps on a 1 Mhz signal no algorithm will be able display noise instead of the aliased signal. In fact sampling 1 MHz @200 ksps would give you a 0 Hz aliased signal, i.e. a DC offset :) I think you are confusing two different issues, interference patterns on the screen and RF aliasing. The latter cannot be fixed by algorithms. If you believe otherwise write a function that shows you are correct. |
| marmad:
--- Quote from: zibadun on July 07, 2013, 05:22:53 pm ---Agilent does this by first estimating the highest frequency component in the measured signal and then selecting a sampling rate which is fast enough to prevent aliasing. The captured samples are displayed using a technique you describe to avoid moire patterns on the screen. Rigol does the same thing more or less. I uploaded an example of this which you simply dismissed ;) If you override scope settings and force 200 ksps on a 1 Mhz signal no algorithm will be able display noise instead of the aliased signal. In fact sampling 1 MHz @200 ksps would give you a 0 Hz aliased signal, i.e. a DC offset :) I think you are confusing two different issues, interference patterns on the screen and RF aliasing. The latter cannot be fixed by algorithms. If you believe otherwise write a function that shows you are correct. --- End quote --- Sorry, man, but I think you're the one who is confused. ;) Both about what Agilent is doing - and about what I've been talking about. And NO, the Rigol is NOT doing the same thing as the Agilent - the problem is that the Rigol has user-selectable sample lengths - the Agilent does not. And it seems Rigol didn't figure out an elegant way to deal with this (e.g. forcing the sample length to a specific size). The Agilent X-Series doesn't 'select a sampling rate' at all - it always samples at the same speed: e.g. 2GSa/s (in the case of the 2000X) - and just varies how many samples it decimates based on the horizontal scale. I NEVER said that the Rigol could anti-alias a 1MHz signal by just sampling at 200kSa/s - I only used the image as an example of the Rigol not performing anti-aliasing. But you can show the exact same failure of the Rigol using any signal (like the attached image of an aliasing 100kHz sine @ 100kSa/s with ANTI-ALIASING turned on). What should happen when you turn on anti-aliasing? The Rigol should be over-sampling (e.g. 2GSa/s) and randomly decimate to simulate 100kSa/s (or whatever your fixed rate should be) - just like the Agilent. Again - I don't need to write any function to see how it would work because I understand the math - if you don't, sorry, but it's not my problem. :) If you don't think it's possible, you should be getting an Agilent owner to prove me wrong. For example: @Hydrawerk - can you please demonstrate? For example, send a 100kHz sine into the DSO - and adjust the horizontal scale until the sampling rate shows 100kSa/s - then grab a screen shot and post it here? |
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