I want to know what good for is that Bandwidth in a DSO

[pc1966]

Not sure what the top speed of commercially available crystals are. They used to top out around the 300MHz region but I suspect that and higher are now using SAW resonators instead.

 

[pc1966]

- Beside >signal decoding<, what else is very important to have?

Sadly I would have to now say "A sane user interface"

Especially for automation line.
or this is the most important function next to a common sampling of a waveform?

It really depends on what you are trying to do. If you are analysing digital signals then logic analyse features like triggering on a pattern are useful, for serial comms the ability to recognise and decode common formats, etc.

If working on audio and low frequency stuff then good bandwidth-limiting options, and also CAT-III probes if working on AC power circuits!

Size of display, battery/portable, etc are other factors. For many a PC adaptor and "virtual scope" is better so data can be captured and analysed, but then you have issues of long-term support as operating systems change, etc.

 

[pc1966]

Back you the OP's first question, then I would probably take the cheapest one as it is 200MHz and fastest.

4 channels is potentially very useful for logic, but remember many 2ch scopes can at least have an external trigger so you can look at 2 independent-in-time signals as well. However, prices is very much more. More importantly they seem to allow you to add ($200) a digital capture 16-channel thing for digital logic analysis.

It is easier to chose for a very specific job, as otherwise you can't tell if you would need faster in the future or more channels.

Ultimately you pay your money and take your choice!

 

[pc1966]

Just to add - if you do get one of the logic analyser sort of add-ons be very careful to only use it on well-behaved low voltage logic. Typically they have very limited protection against over-voltage!

 

[_q12x_]

Well, I already have a DSO138 for experimenting so far. I have it for 3 years or so.

What I dont like on it: It has a very unclean waveform, full of jag and stairs and noise. Not at all clean.
Then, I recently find out it is not suitable to measure logic IC's, so under its minimum limit of 10us.
I dont use it THAT much so a better osciloscope will most probably catch dust for a good percentage of time.
But it will be cool to have one though.
Very good explanations and I really enjoy reading them, very nice lecture to read.
I still have no idea what to choose. Haha.
I guess, the bottom line is... choose one, and live with it.

 

[Julie.]

Well, I already have a DSO138 for experimenting so far. I have it for 3 years or so.
View attachment 102652

What I dont like on it: It has a very unclean waveform, full of jag and stairs and noise. Not at all clean.

...

That's a result of the sample rate.

Misunderstood effects of this do lead to missing key information.

I have a similar oscilloscope to the ones you are looking at, actually a siglent sds1000, it is usable - but you do have to be aware of limitations, when looking for a signal, don't just leave it on the same timebase, apply the signal then sweep through. You get one picture on one timebase and a totally different one on another!

 

[pc1966]

At times i have made simple RC or op-amp filters just so I can keep the scope display to the low frequency signal as I knew there was a lot of HF that would just upset things.

With the older analogue scopes you got a more complete/less strange display under those conditions.

 

[pc1966]

I have a Keysight EDUX1002A which is OK, though now obsolete/replaced by something in darker plastic. Not so expensive I worry about using it.

I also have a Rhode & Schwartz RTB2004 which is far more capable, but also going to be painful if I trash it.

 

[_q12x_]

Does exist in this big world second hand oscilloscopes at lower prices than the new ones?
I never find them, maybe you can direct me to some websites that you may know. Doesnt matter what country they are. Just to be cheaper than the new ones.

 

[pc1966]

I don't know, you could try the usual market places, etc.

Sometimes universities will have old stuff they get rid of when a budget allows replacement but often they are really old and sometimes they just get put in cupboards "just in case". But it might be worth asking.