Products > Test Equipment
Sub: Rigol's DHO800 Oscilloscope (Gibbs Effect & Aliasing Misunderstanding)
ebastler:
To the moderators (I will report this post to aks for their consideration):
Any chance the discussion from reply #1602 onwards could be moved to a separate thread? This thread is getting very long and hard to keep track of anyway, and the several pages of philosophical discussion on pulse response have nothing to do with the DHO800.
EDIT: And it's done. A big "Thank-you" to the moderators! :-+
mawyatt:
Probably a good idea. The discussions involving Nyquist, Gibbs, and Causality perked our interest from way back when we turned Nyquist around into an ally.
Best,
nctnico:
--- Quote from: mawyatt on October 27, 2023, 05:50:24 pm ---
--- Quote from: TimFox on October 27, 2023, 05:27:37 pm ---Of course, the output waveform of a "fast" square wave (e.g., the output of a good binary flip-flop) passed through an elementary low-pass filter (e.g., a simple one-pole R-C circuit) should not exhibit the Gibbs phenomenon on a high-bandwidth analog oscilloscope or a fast-enough sampling digital oscilloscope.
--- End quote ---
Will throw this out for discussion, altho deviating from the DHO800, but seems lots of folks are involved, so maybe worthwhile.
Think it can be stated that ANY system described by continuous domain IIR Response of ANY kind, be that low pass, band pass, high pass, ANY combinations of poles and zeros, or whatever can NOT exhibit the Gibbs effect on an ideal squarewave.
--- End quote ---
I agree. Gibbs effect is about approximating a square wave by adding a series of sine waves which is what the sin x /x function starts to struggle with at some point (say a math problem). Showing a square wave in a bandwidth limited form is different; there simply is not enough bandwidth to display all the harmonics (say a physics problem). IMHO these are two entirely different issues and should not be confused.
Mechatrommer:
i should have provided a "literature" instead of putting it out my broken english mouth... :palm:
https://resources.altium.com/p/how-gibbs-phenomenon-produces-measurement-artifacts
--- Quote ---Therefore, the Gibbs phenomenon is not something that actually happens in a band-limited channel, it’s a mathematical problem that could be easily mistaken for a real effect or could mask a real effect.
...
To summarize, Gibbs ringing is entirely an artifact of your measurement instrument and Fourier/Laplace transform operations on bandlimited network parameters
--- End quote ---
--- Quote from: ebastler on October 27, 2023, 05:59:05 pm ---To the moderators (I will report this post to aks for their consideration):
Any chance the discussion from reply #1602 onwards could be moved to a separate thread? This thread is getting very long and hard to keep track of anyway, and the several pages of philosophical discussion on pulse response have nothing to do with the DHO800.
--- End quote ---
that will be a "task" for the mods... i believe there is already long discussion on these subject in a siglent thread, i thought these all are sorted out among siglent enthusiasts, but i guess not, they came here with false "attack" on signal accuracy and aliasing and all etc... :phew:
Serg65536:
--- Quote from: Mechatrommer on October 27, 2023, 05:32:10 am ---5) you yourself demonstrated the gibbs ear by showing 2c captures, one is using X, another is sinc interpolation, but it turned out you are looking at the wrong side (the actual
--- End quote ---
That's definitely the sinc interpolation effect! On this scale it shows only 100 samples per screen. Ripple waves are exactly between the real samples.
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