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REVIEW - Rigol DS2072 - First Impressions of the DS2000 series from Rigol
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Teneyes:
Hi All
 I am hopeful people can understand this topic and make comments

  To address a question from VE7XEN on the Math Function  Diff()
The manual states:

"Calculate the discrete time differentiate of the selected source.
 You can use differentiate to measure the instantaneous slope of a waveform."

This is somewhat true, but NOT very useful
First it is not the waveform but the display trace that is differentiated
Next the "discrete time " interval is fixed at the sample rate , and not configurable ( delta T)
Next the "instantaneous slope" is always a step in digital sampling resulting in only spikes
Next the scaling is complex to understand.

To demostrate with some displays:
Display 1.  An input of a Triangle signal , should differentiate to a Square wave
                but show ?????  5VU

Display 2.  An input of a Triangle signal , should differentiate to a Square wave
                at a Low level (100mV) to show the discrete pulses

Display 3.  An input of a Triangle signal , should differentiate to a Square wave
                at a Lower level (200mV) to show less the discrete pulses

Display 4.  An input of a Triangle signal , should differentiate to a Square wave
                at a even Lower level (500mV) to show a few the discrete pulses that match the
                steps in the displayed traces

Display 5.  An input of a very slow Triangle signal , should differentiate to a Square wave
                at a even Lower level (500mV) to show a few the discrete pulses that match the
                steps in the displayed traces
                Note: the steps are Not from the generator, 
                         the ramping was accurate to be better than 150uV/6ms

Now, I think this implementation of differentiation is simple and Useless i!!
The question I have for members,
What is a better way??
   Use sample data (more than just the 1400 points of the display data
   Allow high res data, when selected On) ?
   Allow adjustable differentiation intervals ?
   Interpolation between calculated points  ; d(V)/d(t)?
   Process calculate points with smoothy, box car average on results?



tinhead:

--- Quote from: Teneyes on July 15, 2013, 09:39:39 am ---What DSO do you Have ? a Tekway??

--- End quote ---

currently no DSO, but it's not that i forgot already how they work (and i don't mean now Tekway as they new on the market and actually copied what Tektronix is doing) and what they displaying while in FFT.
Carrington:
Wow with a homemade 1K probe, I have obtained a rise time of 1.25ns on a DS2202.  :)  :-+
rf-loop:

--- Quote from: tinhead on July 14, 2013, 12:24:10 pm ---
--- Quote from: Teneyes on July 13, 2013, 07:49:59 pm ---FFT



--- End quote ---

wondering a bit about that picture, FFT center is 3kHz (so full span 6kHz) but FFT sample rate 10kSa/s ? That didn't make any sense. Or is that zoomed in and moved to left side?

--- End quote ---



Here is cheap Owon for around this same.
10kSa/s (original center of course 2.5kHz (0-5kHz)
Then shifted center to 3kHz.
After then zoomed in. (Owon keeps ofd course user adjusted center when zoom in for more narrow span in display)
Signal 3kHz with FM modulation. Mod freq 50Hz.
(Signal produced  by Siglent AWG - so signal itself is far far better than device what show it)




Same but now 300kHz mod FM and modulating freq 5kHz
1MSa/s, shifted for 300kHz to center and then zoomed in.



And then just also for fun.


 

162kHz. First DSP (double sideband) with + and - 3kHz sidebands (3kHz mod)
and last just same with AM (carrier + 3kHz sidebands and 50% mod depth.

Shifted horizontally so that 162kHz center and then zoomed in.
(whole FFT is of course 0-500kHz (1MSa/s)

Only strange is: what is Rigol doing and why? 10kSa/s but full FFT span 0 - ? is it really not 5kHz?

If compare to Owon result... why so big difference? With this resolution it do not see noise floor between 50Hz peaks in two first images.
But about this displayed center, of course "center" is where user have adjusted it. So I can not see any strange there in Rigol for this. Just normal shift-zoom etc. User adjusted as he have want. (between natural limits (but why 6kHz)



cthree:
It's unfortunate that all of this discussion of the 2000 series scopes is contained in a single 104 page thread.
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