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Topic: What Vpp accuracy to expect from oscilloscope and Auto or Single? (Read 872 times) previous topic - next topic

alexmg2

Hi All,
briefly: I have purchased my first oscilloscope yesterday, RIGOL DS1054Z, before that I had friend's SIGLENT SDS1102CML for about a month, now I am trying to switch to using mine and there are some differences in measured numbers when it comes to measuring same circuit (max and min voltages as well as Vpp), I am not sure now which oscilloscope has better accuracy, if this is the accuracy I should expect at all from an oscilloscope of this class and whether I even measure it properly.

now in detail:
For self-education purposes and out of curiosity I am testing different 3.3V voltage regulators that I built based on different chips, different input/output capacitors types and values, different inductors, etc... Then I test them in the same circuit under same load and observe waveform fluctuation, noise.
While I was using my friend's Siglent one regulator was showing only 60mV Vpp, when I measure it with Rigol it shows 120mV Vpp. The measuring parameters are the same, 1mS time scale , 500mV voltage scale. They also detect MAX and MIN voltages differently, siglent showing one numbers while Rigol showing slightly different numbers. I switched probes between scopes but result still the same.
(you can see the illustration below)
So my question is, is this normal to have slightly different readings between two scopes, how do I determine which one is showing more correct measurements? Does this seems correct to you at all?

Also, accuracy of measurement with Rigol seems to improve when I switch it to Single mode, what I do, is I switch it to single mode and push "force" button, so scope capture one waveform and then Vpp is less, is this how you suppose to take your measurements? Asking because normally I would just keep it in Auto and simply watch numbers change or push Stop when needed, but I am wondering if that's not the proper way to capture data?

PS: Again, this is my first real scope so I am just starting to learn it, I apologize for the grain of unprefessionalism and if I use wrong terminology or do something wrong with it, that's why I am asking here :)







alexmg2

Got answer form somewhere else that I am measuring wrong thing, need to set coupling to AC and get closer look at waveform. Thanks all.

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