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| Trying to display bandwith via Math on Siglent SDS2k+/2kHD/800X HD |
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| tv84:
--- Quote from: gf on May 19, 2022, 08:34:16 am ---Even better were a user-adjustable FFT window position, with proper graphical visualization. --- End quote --- That would be the best solution! Shouldn't be any rocket science and it would be very educational (for all users). As it's usually implemented (without any of that info/choices) only experts like you guys are able to talk about it and have a real critic opinion of what is being shown. And as we been reading, even for you guys it's not easy to understand the factors behind what you are seeing. |
| 2N3055:
--- Quote from: gf on May 19, 2022, 08:34:16 am --- --- Quote ---But there is no upsampling. --- End quote --- Performa01 got a 10x higher "virtual sample rate", though, in the screenshots above, when averaging acquisition was enabled. I actually don't see how points with different arbitrary time could be averaged, so a re-sampling to a common regular grid (at higher resolution, say 1/10 sample) makes sense to me. Then each of the the 10 bins per sample can be averaged. Some bins may still remain empty if the trigger point of no trace happens fo fall into their time slot. In order to be suitable as input to operations that need a regular, non-sparse time grid (e.g. FFT), additionaly the empty bins need to be estimated/interpolated and filled-in. --- End quote --- I would call upsampling a interpolation of additional points between real sampled data by virtue of some interpolating math functions from single set of original data. Siglent Averaging acquisition mode will take samples from several (even thousands) of separate trigger events and overlap them on top of each other. It is repetitive interlaced sampling so higher sample rates are very real. As I explained, trigger interpolation IS used to map sampled data to much higher resolution time grid and that is what scope internally has. So sampled data are simply realigned in time and placed in a time grid that is much more granular that ADC sample rate. Such aligned sets of data can be then overlapped on top of each other and averaged. If data is sparse in some places, local to that point averaging will not be as good and there will be larger apparent noise there, worse than for the parts of curve where data is more dense.... But still very useful and big improvement. You are not resampling but simply reassembling the full buffer from separate triggers that are taken with certain offsets from trigger point.. that is why I said "upsampling" is not exactly correct.. Trigger time is not determined. Trigger time is time zero. Exact point of trigger is determined by interpolation and samples are then adjusted to fit in time domain where they belong. Trigger simply starts the process of acquisition, samples are stored in memory, and exact time of trigger event is calculated, and timing of sample points is adjusted. Meaning that timing info of some point in curve relative to trigger point is accurate on a single picosecond level, much less than the sampling period. |
| 2N3055:
--- Quote from: tv84 on May 19, 2022, 09:26:41 am --- --- Quote from: gf on May 19, 2022, 08:34:16 am ---Even better were a user-adjustable FFT window position, with proper graphical visualization. --- End quote --- That would be the best solution! Shouldn't be any rocket science and it would be very educational (for all users). As it's usually implemented (without any of that info/choices) only experts like you guys are able to talk about it and have a real critic opinion of what is being shown. And as we been reading, even for you guys it's not easy to understand the factors behind what you are seeing. --- End quote --- Yes, that would be ideal. Unfortunately not even all high ends scopes have all the controls... In ideal world, a markers should be shown what is being FFT-ed and those markers could be set left and right... I'm not sure how realistic is to expect that on this scope... But it can be optimized to have more predictable behaviour.. It is reported... |
| Martin72:
--- Quote ---In ideal world, a markers should be shown what is being FFT-ed and those markers could be set left and right... --- End quote --- Hmmm...... If I got the time tomorrow, I´ll have a look on the wr9054. Afaik as I´ve played with the fft, I saw "suddenly" 2 dashed lines and wondered because I didn´t had the cursors activated. |
| 2N3055:
--- Quote from: Martin72 on May 19, 2022, 07:00:20 pm --- --- Quote ---In ideal world, a markers should be shown what is being FFT-ed and those markers could be set left and right... --- End quote --- Hmmm...... If I got the time tomorrow, I´ll have a look on the wr9054. Afaik as I´ve played with the fft, I saw "suddenly" 2 dashed lines and wondered because I didn´t had the cursors activated. --- End quote --- As I said, that is a Waverunner 9000.. ^-^ It should support gated FFT... |
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