Products > Test Equipment
Sub: Rigol's DHO800 Oscilloscope (Gibbs Effect & Aliasing Misunderstanding)
<< < (9/48) > >>
tautech:

--- Quote from: EEVblog on October 26, 2023, 11:16:20 pm ---
--- Quote from: ebastler on October 26, 2023, 07:44:02 pm ---Two things are important here, in my view:

(a) It's not the case that the ringing is actually present on the Bodnar pulser's output and the DHO800 somehow "glosses it over" while Siglent shows the truth. Tautech had claimed that early in the discussion a few weeks ago, but dropped that claim later.

--- End quote ---

I showed in my review video two R&S scope responses, MXO4 and RTB2000 and both of them matched the DHO800. The Siglent was indeed the outlier.
The MXO4 is a 1.5GHz bandwith scope, so it should show everything on the Leo Bodnar generator warts and all, yet there is nothing there.
The Siglent clearly has the problem.
I can do more scopes if needed, but if I'm going to trust any scope in my lab it's the MXO44.

--- End quote ---
Mr Bodnar sees otherwise as does my 10 GSa/s 2 GHz SDS6204A.

From Leo's website a capture from a fast Tek clearly displaying the Gibbs ears other scopes choose to suppress.



Better add the falling edge screenshot for the sake of completeness.
Fungus:

--- Quote from: Mechatrommer on October 26, 2023, 11:47:39 pm ---last last time i read you downgraded to 100MHz DHO814 right?

--- End quote ---

Yep.

Measured bandwidth is 200Mhz with the BW7T10 option. I'm not 100% sure what's going on inside the 'scope but I like it...  :)

I don't need 250Mhz so this keeps it a little bit further away from Nyquist. I also enjoy the lack of junk on screen and the perfect calibration.


--- Quote from: Mechatrommer on October 26, 2023, 11:47:39 pm ---aliasing on fast risetime square 10MHz pulse? i suspect you are confused right now. or am i misinterpreting?

--- End quote ---

With 250Mhz+ analog bandwidth and 312.5MSa/sec. sample rate? Yes, you'll get bad aliasing on a pulse.


There's a simple way to know if you're seeing aliasing: Turn some channels off and see if the displayed waveform changes.

(assuming you're not STOPped...)
wasedadoc:

--- Quote from: TimFox on October 26, 2023, 10:53:42 pm ---"Non causal" usually means that the output can chang before (in time) the input does:  not realizable in the time domain.
https://en.wikipedia.org/wiki/Causal_filter
A causal filter's output depends only on past and present inputs, not future values of the input.
Digital filters operating on a data set can be non-causal.

--- End quote ---
It is necessary to compare the relative time of filter input and output.  Agreed the filter output cannot begin to ring before the time of the input transition.  But looking at the output of the Ls and Cs filter there can be preshoot or ring before the main transition.  Perhaps that does not meet the strict definition of "non-causal" but has the appearance of non-causal.  The screenshots under discussion are such.  Only output waveform is shown.
boggis the cat:

--- Quote from: EEVblog on October 26, 2023, 11:16:20 pm ---I showed in my review video two R&S scope responses, MXO4 and RTB2000 and both of them matched the DHO800. The Siglent was indeed the outlier.
The MXO4 is a 1.5GHz bandwith scope, so it should show everything on the Leo Bodnar generator warts and all, yet there is nothing there.
The Siglent clearly has the problem.
I can do more scopes if needed, but if I'm going to trust any scope in my lab it's the MXO44.

--- End quote ---
Have you tried exchanging the probes between scopes?

The probes are part of the measurement system.
tautech:

--- Quote from: boggis the cat on October 27, 2023, 12:22:06 am ---
--- Quote from: EEVblog on October 26, 2023, 11:16:20 pm ---I showed in my review video two R&S scope responses, MXO4 and RTB2000 and both of them matched the DHO800. The Siglent was indeed the outlier.
The MXO4 is a 1.5GHz bandwith scope, so it should show everything on the Leo Bodnar generator warts and all, yet there is nothing there.
The Siglent clearly has the problem.
I can do more scopes if needed, but if I'm going to trust any scope in my lab it's the MXO44.

--- End quote ---
Have you tried exchanging the probes between scopes?

The probes are part of the measurement system.

--- End quote ---
Bodnar pulser connects directly to the BNC channel input.  ;)
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod