Products > Test Equipment
REVIEW - Rigol DS2072 - First Impressions of the DS2000 series from Rigol
Teneyes:
--- Quote from: ve7xen on July 11, 2013, 06:32:48 pm ---. Anyone have any comments on my posts about the MATH functions back here?
--- End quote ---
@VE7XEN eh!
looks like limited numerical , point to point calculation and use DC values see disp
Yes I see Positive accumulations in the Int() function
See pics
1, Dirfting up
2 Drifting down ;D
3 By putting offset of -20mVdc on the 2Vpp sawtooth dirft was zero'ed
4 Now with Sinwave ,
NOTE the input of 7.36Vpp integrates to 4mVpp
the input has a -14.6Vdc Offset
ve7xen:
Thanks Teneyes, I think you're right, it's just accumulation of a constant offset. I suppose that makes sense.
But why the tiny and gigantic values, they're orders of magnitude out from expected?
Teneyes:
--- Quote from: Teneyes on July 11, 2013, 05:44:52 pm ---Reporting A BUG
on FFT the DSO must maintain the Center frequency selected at the center of the display as you change through span scales
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An Update, and very quick, I'm impressed :-+ :-+
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Hello Teneyes (edit)
Thanks for sharing the information. I understand what you are saying - that you would like the FFT function to work more like a Spectrum Analyzer where the span adjusts from the center.
All of our scopes operate like the DS2000 because the high end of the span is really set by the time per division of the underlying signal. That timing effects your sample rate on the display and consequently the max frequency. So, as a design decision we made the span move from the left side to keep the accurate parts of the signal on the display as much as possible.
I would actually prefer that the FFT moves from the center like you suggest, but all our scopes currently move from the left. So, for best operation you may want to move your target signal toward the left side before zooming in or set your span first and then adjust the center.
We will submit this as an enhancement request since we think it is a good idea, but as all of our scopes currently operate in this mode I wouldn't expect it to be something that is changed quickly. We will probably need to put some wider organizational thought into it.
Thanks for the feedback!
Chris Armstrong, General Manager , Rigol NA Technologies
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Hello Chris
Thank you for the quick response.
Yes, I realize the timebase/sample rate sets the max frequency for the frequency span in FFT mode.
I suggest Rigol keep the setup as is.
But I suggest Rigol add a check to see if the Operator-set Center Frequency is within the span of the 4 choices (determined by time base) then I suggest the program does Not go to the pre=assigned Center frequency but keep the operator selected Center Frequency.
Obviously, entering the FFT mode there is no Center Frequency so setting 0 Hz on left is correct.
Now if the time base is Not changed,
then the changing of the Frequency/div does not change the 4 choices(of span) and the Center frequency is still available, so I suggest keep the Center Frequency at center of the Display.
For that matter even if the time base is changed, if one of the new 4 choices(of span) overlaps the existing selection then keep the same Center Frequency .
Thanks Again
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Great process flow summary Teneyes! (edit)
I will pass it along.
thanks for the help making our products better!
Chris
Galaxyrise:
--- Quote from: marmad on July 11, 2013, 07:03:11 pm ---The Rigol does NOT have to do this during sampling; it could sample at full speed (2GSa/s) into sample memory - then do random decimation (to simulate the current sampling rate) to display memory. Of course, this wouldn't work for ALL slower sample rates (at some point the memory wouldn't be large enough), but it could work for many slower rates.
Is this clear now? :)
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With you up to here. I thought "at some point the memory wouldn't be large enough" is every time sample rate is reduced. Going back and looking at one of the examples you posted, the scope is sampling at 200kSa/s because the memory depth is set to 14kpt and the timebase is 5ms. There's no room to increase the sample rate there, so that couldn't be a fix to that particular aliasing. What's an example where it could still sample at 2GSa/s into sample memory that it isn't doing that already?
Teneyes:
A little Tip for Math function Intg()
When using an input from a Chan and the Scan rate is in mSec, then multiply the input by 1000, that way the Units calculated will be in U, see the display
For a square wave input of -1.0 to 1.0 Vdc at 4mSec period
So integrating (+1.0 *1000) for 2 mSec = +2 Units
So integrating (-1.0 *1000) for 2 mSec = -2 Units
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