| Electronics > Beginners |
| Oscillo-confusion MHz GSa/s wfm/s Mpts |
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| tggzzz:
--- Quote from: james_s on January 02, 2019, 07:08:32 pm ---I don't think that's necessarily true. Yes you need a lot of bandwidth to display a really square looking square wave accurately, but the thing is most of the time you don't really need to display it accurately, you just need to understand the limitations of your test gear. Thousands of hobbyists have gotten by with scopes of 20MHz or less debugging digital circuitry. Occasionally seeing the rise time of a signal matters but most of the time you just need to see the pattern of 1s and 0s or see when a signal is changing states relative to another signal. To say someone *needs* x amount of bandwidth is somewhat subjective, more bandwidth is always nice, but you don't need a 400MHz scope to debug an Arduino, a much less exotic instrument will do the job, even if it rounds off the edges of your square waves. Even by the time you get to a 100MHz scope probes and probing technique starts to become an art and IMO it's simply not something a beginner needs to worry too much about. --- End quote --- I first learned the strengths and weaknesses of that approach in 1976, as I noted above in https://www.eevblog.com/forum/beginners/oscillo-confusion-mhz-gsas-wfms-mpts/msg2082310/#msg2082310 In that you will note I designed, built and debugged a computer using test equipment with a bandwidth <1Hz (let alone MHz or kHz!). Hobbyists frequently unwittingly create the conditions in which there are infrequent random failures or failures that take a long time to become apparent. Classic examples: failing to observe data hold times (setup times are comparatively easy), incorrect termination leading to voltage spikes which slowly damage receiver inputs, non-monotonic transitions on clock lines, ground bounce, and several others. If present, those signal integrity problems probably won't be seen on a 20MHz scope. So when their design doesn't work as expected, people will start looking in the wrong place. Seen that far too many times! Once you can be sure signal integrity problems do not exist, then you can concentrate on the "higher level" debugging - and low bandwidth equipment is often completely sufficient. BTW all probing is an art! Even at 50Hz you need to use the right probes for the job, lest you kill your equipment or yourself or someone else. |
| hamiltont:
--- Quote from: tggzzz on January 02, 2019, 06:45:20 pm ---Stackexchange is worth what you pay for it. I'm afraid your understanding is simply and completely wrong. --- End quote --- Thanks for clarifying! It'll take me some time to grok the replies completely, but I appreciate the help - even though I didn't pay for it ;D |
| ebastler:
--- Quote from: FriedMule on December 31, 2018, 09:50:42 pm ---How important would you mean that 4CH is compared to 2CH for everyday use? I think that a later 4CH analog scope could be a good addition? --- End quote --- A lot of good info in the above posts. But I don't think the following point has been made: For me, 4 channels are much more helpful in a digital scope than in an analog one. If you have repetitive signals (for which an analog scope works well), you can always work around the 2-channel limitation by using one channel as the "reference", then looking at various other signals in the second channel, one after the other. In contrast, for on-repeating signals or rare events involving more than two signals, you do not have the opportunity to look at the signals successively. That's where a digital scope shines, and that's where only a 4-channel digital scope will help if you need to look at more than two signals. |
| james_s:
Yes but on the same note even a state of the art scope is not a silver bullet. You could have a 10 GHz scope and still if you are not using it properly it will not tell you what you need to know. Throwing money at the problem beyond a point is usually not the best solution, there is no substitute for understanding what you are trying to do, the limitations of your test gear and how to use it properly. This is where most hobbyists fall short anyway, and why I say that learning to properly use whatever test gear you have, and understanding its limitations is far more beneficial than obsessing over the specs. Until very recently, a scope with more than 100MHz bandwidth was an exotic and very expensive instrument. In most cases there is simply no need for more bandwidth, and other details will be the limiting factor. |
| tggzzz:
--- Quote from: hamiltont on January 02, 2019, 07:51:19 pm --- --- Quote from: tggzzz on January 02, 2019, 06:45:20 pm ---Stackexchange is worth what you pay for it. I'm afraid your understanding is simply and completely wrong. --- End quote --- Thanks for clarifying! It'll take me some time to grok the replies completely, but I appreciate the help - even though I didn't pay for it ;D --- End quote --- I'm trying to reduce the cost (of your time and enthusiasm) due to misunderstandings :) You have the right attitude, so you will need less good luck. |
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