OWON Oscilloscopes

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 Post subject: Rigol, Owon, Hantek and Siglent samplerate tables
PostPosted: Thu May 31, 2012 11:37 am 
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Joined: Wed May 16, 2012 7:54 am
Posts: 187
Here bottom is eye-opening table:

Red line is drawed so that Nyquist frequency is
same or over than 100MHz.
All frequency components what are over Nyqyist
frequency produce aliases if these components
go to ADC.
Pure sinewave have just one component.
In real life there is not pure sinewaves.
If we take ideal 1:1 square wave its components are
(sinewaves) main frequency + "endless" group of odd
harmonic sinewaves.
Simply it can tell that more fast risetime more higher freq
You see square (or other waveform) and what you see is
sum of these components. But you can be exactly sure
there are these components.

And these components what you do not see on the display
they produce aliases!

If you look square signal what really have example 5ns risetime but its
frequancy is 100kHz. One cycle in this signal is 10us.
If use 1us/div there is 5div bottom and top on the screen.
Now try measure signal risetime.
We want realtime or even single shot.

Rigol: 1us/div maximum available samplerate is 100MSa/s
It mean 50MHz Nyquits, it mean 10ns sample period!
Total fail and high amount of corner wobbling
due to sample period related to real risetime in signal (aliasing)

Owon: 1us/div maximum available samplerate is 1GSa/s
It mean 500MHz Nyquist, it mean 1ns sampling period.
It can do this easy and perfect.It can do it also with 2 channel (500GSa/s)

Hantek: 1us/div maximum available samplerate is 400MSa/s
It mean 200MHz Nyquist, it mean 2.5ns sampling period.
It can do it moderate and just acceptable.
With 2 channel there is maximum available samplerate 200MSa/s
It means 5ns sample period and it i not enough for 5ns risetime signal.
It produce aliasing and it can see as corners wobbling in square.

If you need look fast edge signals you need think how fast oscilloscope
you really need!
It need think oscilloscope risetime AND sampling resolution and specially
if signals are not repetive you need look only realtime "single shot"
Thumb rule: If you want 10MHz square wave looks "square wave" on the screen you need
100MHz oscilloscope. And if you need realtime look carefully sampling speed is enough with
these settings what need with yoour signal under test.
Do not look only these "up to" or "max" values what sales peoples want talk.

Looking this table clearly also show that 200MHz Hantek have very bad samplerates related
to 200MHz analog BW. Really bad. It can just do it with one channel in use and 2-200ns/div
and only with small 4k memory.
(1GSa/s is usable only with 2-8ns/div with 4k memory! Yes it can barely be 200MHz realtime
oscilloscope if really stretch thinking and accept this level of "up to" claim. )

Table: Yes it is just like cat with mouses.

Image text is littlebit wrong.
Rigol 100MHz model have 2ns/div setting.
(but it do not affect samplerate)

Here also Siglent SDS1000CML/CNL samplerates


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