Electronics > Beginners
Oscilloscope bandwidth - is jump from 100MHz to 200 MHz significant?
IDEngineer:
--- Quote from: tggzzz on March 05, 2018, 11:01:22 am ---Just so, but it is worth knowing the conditions under which you do need more bandwidth, and the consequences of having less bandwidth. There is no substitute for bandwidth.
--- End quote ---
I'd argue the other way. In many circumstances you can mentally compensate for insufficient bandwidth. But you cannot "fake" your way to a missing third/fourth channel - they're either present or not. Sure, theoretically you can use two scopes with a shared external trigger... but then you still can't compare phase on a single screen across all four signals.
Bandwidth rolls off gracefully. A lack of channels is a brick wall. IMHO always buy four channels, and then get as much bandwidth as you can afford. (Of course there will always be edge cases where this rule doesn't apply, I'm talking about the generic "I need a single scope for all around use" situation.)
tggzzz:
--- Quote from: IDEngineer on February 12, 2020, 04:29:35 pm ---
--- Quote from: tggzzz on March 05, 2018, 11:01:22 am ---Just so, but it is worth knowing the conditions under which you do need more bandwidth, and the consequences of having less bandwidth. There is no substitute for bandwidth.
--- End quote ---
I'd argue the other way. In many circumstances you can mentally compensate for insufficient bandwidth. But you cannot "fake" your way to a missing third/fourth channel - they're either present or not. Sure, theoretically you can use two scopes with a shared external trigger... but then you still can't compare phase on a single screen across all four signals.
Bandwidth rolls off gracefully. A lack of channels is a brick wall. IMHO always buy four channels, and then get as much bandwidth as you can afford. (Of course there will always be edge cases where this rule doesn't apply, I'm talking about the generic "I need a single scope for all around use" situation.)
--- End quote ---
Well, that's a necropost!
The answer is "it depends on what you are doing", and what other equipment you have. You aren't limited to a single tool.
Basically I've found that in the analogue domain 2 channels plus a trigger are neccesary and sufficient. But in the digital domain 4 channels are woefully inadequate; you often need ~16 channels.
So, use the right tool for the job:
* use an (expensive) scope to do measurements in the analogue domain. Only a scope can assess logic signal's integrity and you simply cannot mentally fill in the "missing" bandwidth
* thereafter flip to using a (cheap) logic analyser in the digital domain. You will have far more than 4 channels, and triggering/clocking/filtering are a far better way of ignoring irrelevant signals
IDEngineer:
--- Quote from: tggzzz on February 12, 2020, 05:07:48 pm ---You aren't limited to a single tool.
--- End quote ---
That's just the point: Beginners (who are often the ones asking questions like "What scope features should I buy?") don't always have a lab full of equipment. For you and me, sure. But I remember when I was a teenager just starting out... my "bench" consisted of a scope and a multimeter. Period. No 16+ channel logic analyzers, no multiple scopes at the ready. For folks like that, buying their first and (for a while) only scope, I think more channels is more important than a little more bandwidth.
Just my $0.02. YMMV. Standard disclaimers. Etc. There's no obvious correct answer to questions like this, I was trying to genericize the best possible.
tggzzz:
--- Quote from: IDEngineer on February 12, 2020, 05:19:58 pm ---
--- Quote from: tggzzz on February 12, 2020, 05:07:48 pm ---You aren't limited to a single tool.
--- End quote ---
That's just the point: Beginners (who are often the ones asking questions like "What scope features should I buy?") don't always have a lab full of equipment. For you and me, sure. But I remember when I was a teenager just starting out... my "bench" consisted of a scope and a multimeter. Period. No 16+ channel logic analyzers, no multiple scopes at the ready. For folks like that, buying their first and (for a while) only scope, I think more channels is more important than a little more bandwidth.
--- End quote ---
Hint: look at my .sig!
Anyway, lucky you. I started out with a multimeter, some switches, some LEDs, some potentiometers, and components de-soldered from surplus equipment.
That was sufficient to create this, and later a 6800-based computer with 128 bytes of RAM and a 16-byte ROM made from 16-to-1 multiplexers. I debugged that with a logic analyser made from LEDs and resistors, and used a scope once to check the signal fidelity of the 6800's clock input.
So spare me the lectures about not having much.
Doubly so since a cheap but useful LA can be bought for a few pounds.
IDEngineer:
Hey, this isn't a pissing match. Obviously I wasn't born with a scope in my bassinette. {grin} I was simply pointing out that not everyone has a bench full of gear. True for you at one time, true for me as well, true for everyone. We all start somewhere.
We each have our opinions. We're sharing them here. That's the benefit of a forum like this. Hopefully the OP reads everything, considers his own situation, and makes a (more) informed choice for himself.
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