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New Rigol HDO1000 12-bit DSO - BUGs
gf:
--- Quote from: ebastler on January 02, 2024, 12:38:46 pm ---Also, strangely there never seems to be an FFT data point right at 1 kHz;
--- End quote ---
The FFT frequency points should be integer multiples of delta_f. So with delta_f=20Hz, yes, there should be a point at 1kHz. Strange if not.
EDIT:
Ist it possible that we do not see a 500,000 point FFT, but rather a 524,288 (power-of-2) point FFT?
Then the actual delta_f would be 19.073 Hz, and frequency points would exist at 991.82 and 1010.9 Hz.
This would at least imply that the reported delta_f (RBW) is wrong/misleading.
(The reported number of FFT points can't be wrong, since it is not reported >:D)
EDIT:
Figure.png shows what to expect from a 10MSa/s, 524288 point FFT with Hamming window and linear interpolation.
It also does not match the shape in your screenshot.
EDIT:
And figure2.png show what to expect with 500000 points.
Since 1kHz is an integral multiple of 20Hz, no side lobes are visible.
ebastler:
You might be onto something there! Here's the FFT of a 991.82 Hz signal -- looks nice and symmetrical, with a data point right in the center of the peak. (Although the horizontal scale thinks it's peaking at 992.2 Hz, for whatever reason.)
On the other hand, the frequency step does not match that assumption: I chose that odd span setting in the screenshot to show that the FFT data points are pretty exactly 0.775 Hz apart, corresponding to a record length of 1.29 seconds or 1.29 MPts at 1 Pt/µs. What kind of number is that though? Not a power of two... And actually more than the advertised 1 MPts. Mysterious...
EDIT: At least I figured out what went wrong at 50 ms/div and slower in yesterday's experiments. I had the acquisition mode set to "Roll: Auto", with a 50 ms/div threshold. I just never noticed the rolling trace, since it was a steady sine with individual periods not resolved on the screen. Easily avoided, but it would be nice if the FFT were not bothered by that acquisition setting.
Antonio90:
--- Quote from: centauro1954 on March 01, 2024, 07:35:48 am ---Good morning,
have you tried activating a video signal? (pal/secam)my DHO1074 can't trigger a video signal
--- End quote ---
Hello, yes, it is a known bug, and a software problem with the platform in general. You will have the same problem with any DHO1000, even if you get it exchanged by the seller.
People interested in this oscilloscope model will read most, if not all of the related threads, no need to post in all of them.
Alex-lab:
Some new weird behaviour.
I was trying to analyse a saturation limit of the inductor. Blue line is the current (1Ohm).
However, when I changed Y-scale, the pulse changed its shape with some negative spike.
Any hypothesis? Thanks.
Fungus:
It could be you're going way off the bottom of the screen, in which case you're running into opamp overload/recovery.
Does it change if you move the trace up/down?
Zoom in horizontally to take a good look at the negative peak.
There are many threads on this topic, eg.: https://www.eevblog.com/forum/testgear/rigol-ds1054z-vertical-distortion-problem/
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