Products > Test Equipment
REVIEW - Rigol DS2072 - First Impressions of the DS2000 series from Rigol
pa3bca:
--- Quote from: marmad on November 09, 2014, 04:27:46 pm ---
Except, as I've already posted extensively about, the DS1000Z does NOT do correct 12-bit High Res at all. So you're basically just looking at a brighter waveform that is barely (if at all) being averaged. I just checked Roll mode on both scopes (@ 200ms/div), and the DS1000Z is definitely not averaging to 12-bits (i.e. no High Res) - while the DS2000 does it perfectly.
--- End quote ---
Yes I realize(d) the difference between the scopes. But it does not explain (at least not to me) why the wave intensity of the (signal) trace on the DS2072 drops of instantly and dramatically when the timebase is > 100 ms/div - becoming almost invisible.
marmad:
--- Quote from: pa3bca on November 09, 2014, 04:40:35 pm ---Yes I realize(d) the difference between the scopes.
--- End quote ---
But then running the DS1000Z in High Res/Roll is almost equivalent to DS2000 Normal/Roll, so why bother swapping scopes? ;)
--- Quote ---But it does not explain (at least not to me) why the wave intensity of the (signal) trace on the DS2072 drops of instantly and dramatically when the timebase is > 100 ms/div - becoming almost invisible.
--- End quote ---
I believe the dimness of the waveform in High Res mode at slower timebases comes from the interaction between the successive sample averaging and the decimation for the intensity buffer. I think that it's actually performing correctly - in terms of the intensity mathematics (every 256 successive samples are being reduced to 1) - but it's the kind of thing that, even though technically correct, does not lead to a good visual result. It would require a workaround in the code to bypass (or correct, depending on your point of view) the problem.
pa3bca:
--- Quote from: marmad on November 09, 2014, 04:47:15 pm ---But then running the DS1000Z in High Res/Roll is almost equivalent to DS2000 Normal/Roll, so why bother swapping scopes? ;)
--- End quote ---
Well I wanted to look at a low frequency signal with a lot of noise on top - including scope noise as I was at nearly maximum sensitivity. Hires gets rid of a lot of the noise. But then this signal becomes nearly invisible on the 2000.
The 1074 hires mode also gets rid of some of the noise, not as well as the 2000 but at least the trace is better (visible)
--- Quote ---I believe the dimness of the waveform in High Res mode at slower timebases comes from the interaction between the successive sample averaging and the decimation for the intensity buffer. I think that it's actually performing correctly - in terms of the intensity mathematics (every 256 successive samples are being reduced to 1) - but it's the kind of thing that, even though technically correct, does not lead to a good visual result. It would require a workaround exception in the code to bypass (or correct) the problem.
--- End quote ---
Hmm but why the sudden change @ 100 ms/div. I would expect a more gradual dimming.
marmad:
--- Quote from: pa3bca on November 09, 2014, 05:00:58 pm ---Hmm but why the sudden change @ 100 ms/div. I would expect a more gradual dimming.
--- End quote ---
The acquisition/display engine is working differently at the slower timebases. You can see that when you're at <=100ms/div, the entire waveform is captured before being displayed (i.e. all decimation is done), but when at >=200ms/div, it is displaying the waveform AS it's being captured (i.e. decimation done on the fly - thus not being affected by subsequent captures).
The Rigol's do intensity grading based on BOTH vertical and horizontal overlapping from sample to display memory. When displaying on the fly (anytime you're running at >=200ms/div), the overlapping (and thus, grading) will be different since it won't know beforehand the upcoming samples. This is true on the DS1000Z too, but because it's not really doing 12-bit averaging, you don't see the intensity difference caused by the missing (averaged) samples when displaying on the fly.
EDIT: BTW, this could explain why Rigol doesn't do true High Res on the DS1000Z: because people complained about the dim waveform on the DS2000 when using it at >=200ms/div, so instead of finding a workaround, they just crippled it on the DS1000Z. ;) I suspect it's either that - or the engine is just not fast enough for it.
pa3bca:
--- Quote from: marmad on November 09, 2014, 05:11:10 pm ---The acquisition/display engine is working differently at the slower timebases. You can see that when you're at <=100ms/div, the entire waveform is captured before being displayed (i.e. all decimation is done), but when at >=200ms/div, it is displaying the waveform AS it's being captured (i.e. decimation done on the fly - thus not being affected by subsequent captures).
The Rigol's do intensity grading based on BOTH vertical and horizontal overlapping from sample to display memory. When displaying on the fly (anytime you're running at >=200ms/div), the overlapping (and thus, grading) will be different since it won't know beforehand the upcoming samples. This is true on the DS1000Z too, but because it's not really doing 12-bit averaging, you don't see the intensity difference caused by the missing (averaged) samples when displaying on the fly.
--- End quote ---
Aha! Now it makes sense. From 100 -> 200 ms/div the display indeed changes from complete capture -> display to displaying "live" while capturing.
Thanks, this helped me a lot. (Still would like Rigol to do something about it, but it is probably not on top of a list)
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version