Robin Oswald

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  1. @MalcolmBased on my adventures using the NA, I'm very confident that it should give you reliable results for the scenario shown in your screenshot, especially because I can still rather easily see the sine wave in the response by eye and can pull out a phase difference if really required. I've seen the AD pull out reasonable mag/phase from a lot worse time traces! The only thing that is a bit borderline (but probably still acceptable) is the amplitude of the blue channel being only a few mV. For your scenario, this should still work, but to improve the measurement it'd be advantageous to
  2. Hi @attila 1. Did anything else change (i.e. triggering, synchronization, etc.)? In my first post the default averaging didn't seem to help, which started all of this. 3. Thanks, I'll check it out! 4. Windowing If I understand things correctly, then the main reason why the flat-top window is popular in applications such as FFT analyzers etc. is because of the flat-top, which will make sure that the measured amplitudes are correct, regardless of being unlucky with the spacing of the FFT bins. I.e. if there are bins at 1 kHz, 2 kHz, 3 kHz etc. and we have a sine wave at 1.5 k
  3. Hi @attila I've finally gotten around to testing coherent averaging in the lab, both with my basic test setup consisting of the differential amplifier, and with real-world applications such as characterizing feedback loops in-situ. Overall, I'm very happy, and it works beautifully. Thank you so much, this is very useful! Example 1: Basic test using differential amplifier For the following setup (same as in initial post): I now get the following measurements (for different averaging modes, number of averages, windows, etc.): Note how the y-axis for the magnitu
  4. Hi @attila Thank you very much, I'll give it a go (not sure if I'll manage this week, or if it will be next week).
  5. (short answer because I have to run to a meeting): Another reason that just came to my mind why the coherent averaging might not work as well as expected is the order in which the measurements are taken. Essentially it boils down to reversing the order of the two for loops in my pseudocode above, which will make a big impact depending on coherence times between W1 and W2: Scenario A: Average first, and then move on to the next frequency If I'm not gravely mistaken, then this is what is currently implemented. Crucially, if W1 and W2 have decent coherence on the time scale re
  6. Hi, @attila Thanks for the patience and the more detailed explanations. The fact that the coherence function doesn't look at all like expected indicates to me that we're still missing something. I'd have expected the coherence to be close to 1 everywhere except at the frequency where W2/Wext is active. There it should drop from 1 down to maybe 0.5 or so. However, on the first screenshot above, the blue trace is always near one and never drops. On the second screenshot, it's even weirder with the baseline starting at 0.5 rather than 1, and coherence getting better rather than worse at
  7. Hey @attila, Thank you very much for giving this a shot, and especially for doing so so very quickly! Debugging coherent averaging Based on your screenshots, I agree that the currently observed improvement is mediocre at best. However, from my experience & intuition, I'd expect a much bigger improvement. To me, that leaves us with three main possibilities: 1) My intuition could be wrong Maybe my intuition is not so good after all, or some subtle assumption fails to be met, and what you show really does represent all we can hope to achieve. Currently, I still hope
  8. Hey, First, I want to congratulate you on the Analog Discovery kit & Waveforms software. The hardware is decent, well-documented and affordable (especially before the covid price hike). However, what really makes it stand out for me is the Waveforms software, which simply works well, is modern and convenient to use, and reasonably open and extendable (unfortunately all of these three points are often sorely lacking in test & measurement equipment). As a consequence, this has led my lab to buy a dozen or so ADs over the years. Background Recently, I've started using the netw