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

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Carrington:

--- Quote from: Teneyes on July 01, 2013, 07:20:24 pm ---
--- Quote from: Carrington on July 01, 2013, 06:23:49 pm ---Another curious thing, look at the pictures.
Where is the difference?

--- End quote ---
Yes , I see a picture of 500Mhz Agilent Scope
with a Label of OWON , what is your point??
You like bullshit!!

--- End quote ---

Oh no please do not misunderstand me. Respect please. I'm just saying what I think. Owon is not the best, but recognize that in the image above is nothing short, regarding BW.
Please understand that my native language is not English, so may that I am not express properly.

EV:

--- Quote from: Wim13 on July 01, 2013, 07:07:35 pm ---See picture with a rise time of 1.5 nSec that is 350/1.5  is 233 Mhz,
what is also measured with a signal generator

--- End quote ---

It is even better. Look at the picture, there rise time is 1.32 ns which gives BW = 350 / 1.32 = 265 MHz.

Carrington:

--- Quote from: EV on July 01, 2013, 07:51:43 pm ---
--- Quote from: Wim13 on July 01, 2013, 07:07:35 pm ---See picture with a rise time of 1.5 nSec that is 350/1.5  is 233 Mhz,
what is also measured with a signal generator

--- End quote ---

It is even better. Look at the picture, there rise time is 1.32 ns which gives BW = 350 / 1.32 = 265 MHz.

--- End quote ---

Imagine doing the test (rise time) using this:
http://www.maxim-ic.com/an3699
The result probably be closer to the oscilloscope real BW.

Thanks EV.

zibadun:

--- Quote from: marmad on July 01, 2013, 06:50:36 pm ---
--- Quote from: zibadun on July 01, 2013, 05:43:00 pm ---I think this function changes how captured samples are mapped to pixels on the screen to minimize aliasing.  It doesn't change the way the signal is sampled. It works when scan rate is much slower than the sampling rate.  What did you expect this button to do?

--- End quote ---
Anti-aliasing never changes how the waveform is sampled. But you seem to be thinking about IMAGE anti-aliasing - I'm speaking about WAVEFORM anti-aliasing; which is what a DSO is supposed to do if it has an anti-aliasing feature (it has nothing to do with jagged edges, pixels, etc).

This post and the following one provide more information.

--- End quote ---

 Marmad, I understand what aliasing is.  I don't believe it's a bug or even annoyance if this option does not let you to measure a 1 MHz signal with 200 kSa/s ;)

You need to use a high enough sampling rate for the signal being measured and also make sure that any higher frequency components are cut off with a low pass filter.  There is no way around it.   

May be you are thinking of undersampling when you are actually interested in displaying aliased frequencies.  But this mode still requires proper analog filtering to work correctly..  I bet one cycle of free trial options that  IMAGE anti-aliasing is what Rigol had in mind and it's working as designed. :) 

marmad:

--- Quote from: zibadun on July 01, 2013, 07:57:29 pm ---Marmad, I understand what aliasing is.  I don't believe it's a bug or even annoyance if this option does not let you to measure a 1 MHz signal with 200 kSa/s ;)
--- End quote ---
zibadun: Man, we've been talking about this for ages already here - it's not about measurement; it's about incorrect display. The point is - you shouldn't see a waveform of a lower frequency - you should see (what looks like) noise (see what the 1MHz waveform SHOULD look like at that time base).

And, BTW, it's not just about 1MHz @ 200kSa/s - it's ANY frequency at a slightly lower sample rate - it doesn't work at any level.


--- Quote ---You need to use a high enough sampling rate for the signal being measured and also make sure that any higher frequency components are cut off with a low pass filter.  There is no way around it.
--- End quote ---
Of course there is - Agilent does it. It's actually fairly easy - there are papers written about it (linked in earlier posts in this thread). You just do random decimation from sampled data to display data (e.g. instead of displaying every Nth sample, you vary the decimation). So instead of seeing a FALSE lower frequency, you see NOISE.


--- Quote ---I bet one cycle of free trial options that  IMAGE anti-aliasing is what Rigol had in mind and it's working as designed. :)

--- End quote ---
No - that's not what they had in mind - look at the manual excerpts. It's perhaps what the guy who coded it had in mind, but he FUCKED UP! It's a bug, mistake, or unimplemented feature - there is no way around that fact.



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