Thanks everyone.. doing the best I can here considering my lack of knowledge and experience when dealing with DSOs. I hope to post a video part 2 of extensive use of the firmware - it's MANY problems - and it's few nice features - but first I'm plowing through reading material: Nyquist theorem applied to DSOs; ADC interleave distortion, and, well... most of you know the rest - and I'm also taking notes while running tests to save video recording and editing time later.
I could use suggestions in tests I could run or specs I might check with what I have on hand.... which is very little, I'm afraid. I've gotten by for years with a 30-year old 25MHz Tektronix analog scope, a 10 year-old Fluke DMM, and assorted logic probes, etc. So I don't have a faster scope, spectrum analyzer, etc. Just the Hantek AWG - and of course, I have tons of digital circuitry with which I could generate, at the very least, fast, repetitive clock signals.
But in the meanwhile, here are some screen captures and some of the info I've compiled. The first 6 .pngs are exact comparisons between the Rigol and Owon made using the same test setup with the DDS3X25 and the same settings on the scope (except you'll notice the volts/div is off - on the Rigol the inputs were set to 10x - on the Owon 1x - but the ratio between the channels is the same).
I could not replicate the 75MHz result I had with the Rigol on the Owon. I'm not sure if this is due to the fact that 75MHz from the Hantek is not particularly stable - and I managed to get lucky with the Rigol - or, more likely, problems with the Owon. This was just an averaging issue (as pointed out by saturation) - which I used on the Rigol for the unstable 75MHz, but forgot to do on the Owon.
Although the 100MHz .pngs from the Owon don't look too bad, what is odd is that I have the display set to dots, not vectors, and the sine wave coming from the Hantek is exactly 2 points per period; i.e. a triangle wave. Why is the Owon showing a sine? Is it because I can't turn off sin(x) on the Owon scope? The 2 .pngs after the 100MHz screen caps show the saved 100MHz waveform brought into the Owon PC software - two times saved, one after the other - with different sample points on the waveform. Again, I'm not sure if this is due to the instability of the DDS3X25 at this high frequency, but it doesn't look good to me.
Other data, problems, or issues I've discovered:
No Equivalent Time Sampling available. That kind of sucks - I just assumed all modern DSOs had this - it's very handy for fast repetitive signals in digital circuits.
No way to turn off sin(x) - as mentioned above.
When using the frequency counter (on the trigger channel), the count becomes more and more incorrect the further the trigger level is moved below the zero line of the waveform. As mentioned in another post, I haven't replicated this bug since the first time, so it's intermittent - and not easily - because I couldn't repeat it. So, it's not that important - because you notice it right away when playing with trigger level (and it works fine always when trigger level >= 0).
It takes exactly 4 minutes to save the full 10Mpts to the USB hosted device (during which, of course, the scope is doing nothing else). That works out to a data rate of about 333kbps.
I haven't checked the USB to PC transfer rates yet, but I will. It also takes exactly 35 seconds to save a screen image to the USB hosted device. It takes the PC software about one second to transfer a full 10Mpt record from the scope - a little better than the 4 minutes needed to write it to a USB stick, yes?
That's around 80Mbps, which = 6.5x > full bandwidth USB 1.1 - and about 5x < max. bandwidth 2.0. So it's definitely USB 2.0 as advertised. It's certainly a big improvement over communication speeds with either the Rigol or the Hantek AWG. To recap: the Owon appears to use USB 1.1 as host - USB 2.0 as device.
The 'Copy' button does NOT work to copy screen images to the hosted device - as the manual says it will. Obviously, you can still do it through the 'Save' menu, but this means you can't do screen captures with the different menus displayed. Now I AM getting the 'Copy' button to work as described in manual - so it's a slight bug (sometimes yes sometimes no). I haven't cracked it's logic yet
The screen is gorgeous - not doubt about it - and the VGA output works great and should be on every DSO - but the firmware's usage of screen real-estate in general is not good (which is so sad on an 800x600 display). They don't have split-screen modes for FFT, or, at the very least, for zooming in on waveforms.
The measure functions seem pretty weak to me. You can only have 4 measurements at a time on that massive screen (unless using Show All, which is problematic itself, as mentioned below) - and the procedure you go through to add or remove each one is bad interface design. Also, some of the measurement abbreviations they use are strange and not following standards.Actually, you can have 8 measurements on the screen at one time: it looks like only 4 will fit in the given display space, but when you add a 5th, it pops the Channel and Sample settings out into a different part of the screen (unexpectedly). So, this is actually fine - 8 is plenty in most circumstances - and mitigates the problem with Show All mentioned below. Also, when I was adding measurements before (it uses a 3-tiered menu system), I assumed you had to press the encoder knob (which you turn to select which measurement you want) in order to confirm the selection - and I hate when you have to press encoder knobs to select anything (inevitably the selection often jumps to a different one by the act of pressing) - but this is not the case - so I've started to warm up a bit to the Owon's menu system.
The Show All is annoying, since it blocks much of the screen (see the attached .png) - and it doesn't actually update if you alter settings while it's displayed - it just shows the frozen measurements from when it was invoked. Not much use in real-time situations.
The firmware uses a two or three menu system (bottom menu, then side menu, then sometimes a floating menu on the other side), and although it's handy in a few cases, it's really - from my point of view -
poor less-than-optimum software design.
The Rigol also has some poor design in terms of the menus, but it's at least understandable because of the limits of screen real-estate and buttons. The Owon has 10 dedicated menu buttons - and a massive screen - so there's no excuse (except the obvious - saving money) for not having a well thought out menu system. The menu system has started to grow on me a bit - it's still far-from-perfect (but which DSO is?) - but it's perhaps equally advantageous to disadvantageous (50%/50%) - as opposed to my previous opinion (20%/80%). I have much more to say about it - but will save it for the final video review.
The Owon PC software became EXTREMELY slow then crashed (on my Intel i7 950 Quad-core) when trying to view an entire saved 10Mpt file of a 2.5MHz square waveform all at once (>1ms/div). It worked for a saved 10Mpt file of sampled noise - but not the square wave.
That's all for now.
Edit: Added 'Copy' button bug above.
Edit2: Changed my opinion of the measurement features above. They actually aren't too bad (although the Show All position on screen [and non-real time function] is still rather silly). Also, the menu system seems a little less bad than previously mentioned.
Edit3: Changed notes on frequency counter and 'Copy' button above.
Edit4: Added speed results for USB to PC transfer.
Edit5: Posted a summary of thoughts on Page 3. Video Part2 may or may not come later.
Edit6: Revised comments about 75MHz screen cap and USB speeds above.
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