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New toy(?) scope, DSO154pro, 1ch, claimed 40MS/s

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Fungus:

--- Quote from: Dave_g8 on March 26, 2024, 01:53:24 pm ---
--- Quote from: BillyO on March 26, 2024, 02:12:42 am ---In this video @ 15:40 the bandwidth of the 154Pro is tested and does just fine @ 18MHz.  No where near -3dB.

--- End quote ---
Yes, the analogue bandwidth of the front end is greater than 18MHz.

--- End quote ---

Yep. I've got one, if I put in a 22Mhz sine wave I see a perfect 18MHz sine wave on screen (as predicted).

You need to go up to maybe 28Mhz before you see much attenuation.

Those things are nice little gadgets but aliasing is a big problem even at "Arduino" frequencies.

Dave_g8:
Hi Bill,
If you inject a 1MHz square wave with a faster edge, you will see more of a difference.
The top trace is a Rigol sampling at 1GSa/s and there is no ripple.

The DSO154Pro is fine, but you may not be seeing a true representation of the signal.




BillyO:

--- Quote from: Dave_g8 on March 26, 2024, 05:14:27 pm ---Hi Bill,
If you inject a 1MHz square wave with a faster edge, you will see more of a difference.
The top trace is a Rigol sampling at 1GSa/s and there is no ripple.

The DSO154Pro is fine, but you may not be seeing a true representation of the signal.

(Attachment Link)

--- End quote ---

You are seeing exactly what you should be seeing for a scope with 18MHz bandwidth.  Harmonics above 18MHz will begin to be attenuated.  Your image is showing good contributions from the first 16 or so harmonics.  That is 100% expected for an 18MHz scope.  I am willing to bet the other image comes from a scope with far greater bandwidth.  In this case it has nothing to do with sample rate.  Just bandwidth.

Dave_g8:
Hi Bill.
If you put a 1MHz square wave into a 20MHz analogue oscilloscope, you will not see the ripple as seen on the DSO154Pro.

BillyO:

--- Quote from: Dave_g8 on March 26, 2024, 05:27:12 pm ---Hi Bill.
If you put a 1MHz square wave into a 20MHz analogue oscilloscope, you will not see the ripple as seen on the DSO154Pro.

--- End quote ---
Well, you will but it will be harder to see because of the response of an analog scope.

Here is an image of a square wave composed of the first 16 harmonics.  Does it look familliar?

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