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Siglent SDG1032 Amplitude not constant when sweeping
nctnico:
This sweep is shorter compared to the previous one. For repeatability, don't change the signal settings you are using. Unless you are using an extremely long coax cable, reflections shouldn't be an issue at all. Either way, you should zoom in on the areas which show low amplitude. A potential problem could be the decimation (sample skipping) in the DSO to create the screen causes the signal envelope shown to be lower than it actually is.
eTobey:
--- Quote from: nctnico on May 18, 2024, 10:01:45 pm ---This sweep is shorter compared to the previous one. For repeatability, don't change the signal settings you are using. Unless you are using an extremely long coax cable, reflections shouldn't be an issue at all. Either way, you should zoom in on the areas which show low amplitude. A potential problem could be the decimation (sample skipping) in the DSO to create the screen causes the signal envelope shown to be lower than it actually is.
--- End quote ---
The sweep has the same length. It did not start at 0ms. I had no trigger there.
From the video of dave, i think reflection DO play a role? Your statement conflicts with my understanding of what i learned from the video. Did i got something wrong?
I could not reproduce the waveform on that other picture, but a different one. I have testet it from 10ksa/s to 500Msa/s: The amplitudes stayed the same on the zoomed out view.
eTobey:
This is now the best result i could achieve on the sweep.
Could it be improved by some more measures?
nctnico:
Can you please show 3 screendumps where you can see the actual waveforms at the start, middle and end of the sweep? And make sure that the signal fits on the screen of your oscilloscope vertically? Only then it is possible to understand what is the problem with your measurement.
ebastler:
--- Quote from: eTobey on May 19, 2024, 09:37:14 am ---Could it be improved by some more measures?
--- End quote ---
You should really measure with the probe directly at the generator's BNC output. I am not quite sure from your photo, but it seem like you still have a length of two loose wires as part of your connection, which obviously don't have 50 Ohm impedance and may cause reflections.
There are dedicated adapters for that, e.g. here, or they come included with some scope probes. (I got mine with the Testec probes I bought a few years ago.) But in a pinch you can improvise by plugging the bare probe tip into the BNC jack and making the ground connection with a piece of wire or foil.
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