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I've made a simple inverter circuit and I've read the voltage across the load resistor using a RIGOL DS1104 oscilloscope. Here is the link to the screen capture. I'm using a full-bridge inverter topology, I'm using an Arduino Uno for control, and I have no feedback control system yet in place. I am filtering with a capacitor in parallel with the load resistor as well as an inductor in series with the combination of those two. I'd like to know why my oscilloscope measurement jitters from side to side and how much of a problem that presents to the quality of my sine wave? Thank you!

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    \$\begingroup\$ You'll at minimum need to include a circuit diagram and an explanation of exactly what your code does. There's probably some slower periodic behavior modulating your output (possibly the Arduino timer interrupt???); you might or might not be able to capture that by drastically reducing the timebase and capturing in single mode. Explaining it would take details of the implementation which you have not provided. \$\endgroup\$ Oct 4 '18 at 3:31
  • \$\begingroup\$ Also note how you point to the oscilloscope being the problem while there is no proof that it actually is the oscilloscope being the problem. What makes you believe that your signal is jitter free? \$\endgroup\$ Oct 4 '18 at 6:01
  • \$\begingroup\$ Change the time base, you appear to have some AM going on \$\endgroup\$
    – JonRB
    Oct 4 '18 at 7:01
  • \$\begingroup\$ It would be helpful to add how you did set up your oscilloscope as well as what signal you expect to see and what you actually see on the scope (shape, amplitude, frequency...). \$\endgroup\$
    – Grebu
    Feb 23 '19 at 10:56
  • \$\begingroup\$ I'm voting to close this question as off-topic because it has been abandoned by an asker who ignored requests for clarification and suggested courses of investigation \$\endgroup\$ Feb 23 '19 at 17:50
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There is not a lot of information here, but when I see students with jittery sine waves on their oscilloscope screens it is almost always because they haven't set their trigger level well. If your scope has an "autosetup" try that for now (and learn how to set up an oscilloscope), but in general set the trigger near the zero-level of the scope. At the zero level the rate-of-change of the sine is maximum and the jitter in the display will be minimum.

Edit: Chris Stratton's comment is quite right.

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  • \$\begingroup\$ While this can happen in other circumstances, the situation depicted here is either an actually varying amplitude, or a drastically higher frequency aliasing with the sample rate to give that fictitious impression. It would be worth looking again to notice that that the trigger is rock stable at a central zero crossing; what is changing is primarily the amplitude and perhaps very slightly the frequency, but not the trigger position. \$\endgroup\$ Oct 4 '18 at 3:54
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Per sigmadelta, start by setting the trigger properly, first by trying the AUTOSETUP and see if that improves the display.

My guess is that you'll still see the signal amplitude vary from cycle to cycle, but at least it will trigger at the same point for each sweep. Once you've achieved that, you can determine why the sine wave isn't a constant amplitude. Hope this helps. Send more info if you can.

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I'd guess that "I'm using an Arduino Uno for control" is your culprit. I notice that the amplitude of the output is varying noticeably. Since you say that there is no feedback, and assuming that the raw bridge voltage is remaining constant, I'd suggest that the period of the drive voltage is not constant, and varying the drive waveform is causing the output to vary.

Instead of looking at the output, try looking at the bridge drive waveform. If you see horizontal jitter there, that's your problem. And if that's true, then, "how to fix it" is straightforward: learn to do a better job of programming.

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