Products > Test Equipment
Rigol DHO804 Test and Compare Thread
Martin72:
I think I've figured it out.
At 5ms/div the FFT disappears, correctly because the sample rate is then too low.
But it comes back when enough sample rate is available - from 2ms.
But earlier it didn't come back and the scope was permanently stuck at 12.5MSsa/s.
So don't play around with it too much... ;)
Otherwise, the FFT function behaves in the same way as its big brother, the 4204.
In other words, hardly anything can be set, no different modes, which is a particular pity that there is no averaging.
And what I already noticed in February with the 4204 is also present here.
Generator with wavecombine function, 10Mhz frequency, ch1 10Vpp, ch2 1mVpp 10.1Mhz frequency, 50Ohm termination.
I have done this with another scope with a "flattop" window and it works perfectly.
With Rigol it looks different when you switch from Hanning to Flattop.
ebastler:
--- Quote from: Martin72 on November 30, 2023, 09:08:54 pm ---hardly anything can be set, no different modes, which is a particular pity that there is no averaging.
--- End quote ---
The absence of averaging is clearly a gap. Makes the FFT output so much cleaner, and makes signals clearly visible that you otherwise have to guess at -- and it should be easy to implement. I think it's catching up with Rigol here that they implemented Averaging as an acquisition mode (only), not as a math function. That's a nice solution when you want to use Averaging on time-domain signals: no overhead and conveniently activated. But it means that averaging is not available post-FFT. A dedicated option would be needed there.
Besides that, I am struggling with the "hardly anything can be set" complaint. Span and Center are set directly in the FFT dialog; sampling rate and record length are set via the time base and memory size in my understanding. Are there critical parameters which can't be adjusted at all? Or is the complaint that the settings are not as clear and direct as one would like? -- Not aiming to defend the Rigol scopes here; I would like to better understand what is missing (or awkward). Thanks!
--- Quote ---With Rigol it looks different when you switch from Hanning to Flattop.
--- End quote ---
Looks like the Flat-top window function is plainly broken on the Rigol. It is just that particular window function which gives the unexpected results, right? Maybe they don't deal with the negative weights properly? Looks like a bug.
Fungus:
FFT center and span are really easy to set on a touch screen...
Martin72:
--- Quote ---Besides that, I am struggling with the "hardly anything can be set" complaint.
--- End quote ---
Deepl translation error..
There is nothing to complain about in the menu operation, on the contrary, I think it is one of the most successful menu structures at the moment.
ebastler:
--- Quote from: Martin72 on December 01, 2023, 09:44:54 am ---
--- Quote ---Besides that, I am struggling with the "hardly anything can be set" complaint.
--- End quote ---
Deepl translation error..
There is nothing to complain about in the menu operation, on the contrary, I think it is one of the most successful menu structures at the moment.
--- End quote ---
I didn't understand it as "it is hard to set anything", but as "there are not enough things which can be set". Is there something in the FFT which you would like to adjust but can't?
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