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Old 10-21-2010, 04:09 AM   #1
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Default Need an oscilloscope

So, I need an oscilloscope for a project I'm working on, but I've absolutely no idea what to look for. Budget will be VERY low, so I'm probably going to buy one on eBay.

Anyway, question time.
What brands are good/bad?
What frequency should be adequate for most projects?
Is there any reason to get more than two channels?
Anything else I should look for?


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Old 10-21-2010, 06:50 AM   #2
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Default Re: Need an oscilloscope

you're worrying about the wrong things

good brands and bad brands don't really come into it any more, even the cheapest of chinese scopes are pretty good now-a-days, as feature rich (if not more) than the traditional big players, at a fraction of the price, and they do last well. (at least the reviews I've read suggest that).

it really depends on what projects you're doing as to what frequencies you'll need.
if you're doing audio or radio work then a 20 or 40Mhz, analogue scope would be good enough.
if you're analysing digital stuff then go with a digital scope (that can store and print output as well).

digital scopes are never going to be as good as analogue for analysing analogue signals, and the same is true visa versa. so have a think about what most of your projects will be based around...

(analogue scopes don't work as well for digital because there is no storage features, it's difficult to see what's going on, digital scopes don't work well for analogue projects because they can't 'see' noise as well).

personally, I've had a really old 2 channel analogue scope for ages, 2 channels is enough for most work, but if does really rather depend on what you're doing, and how you work. I've seen some really good prices on some Chinese digital scopes, (few hundred dollars), I've read some good reviews so I'm personally going to do a bit of saving and get myself one. I'll use my scope for analogue work, (ignoring the fact that it's not good for that), simply because I'll still have my analogue scope in case I'm getting some bad noise somewhere I can get that out and have a look.

I'm going to go for either 60MHz or a 100MHz scope, because frankly there isn't that much difference in prince in the cheap chinese ones between 20 - 40, 40 -60 or 60 - 100.

I think it was about $150 difference between the 20MHz and the 100MHz scope, which yes, is a lot, but not as much as finding out that 20 wasn't good enough and really wanting the 100MHz -my analogue scope is 20MHz, but as I said above digital scopes do kinda lack the resolution, so I'm going for a scope with five times greater resolution, hoping that I'll get roughly the same picture that I get for analogue stuff.

Anyway, I drifted off track there...
if you're fault finding, or analysing then generally 2 channels will be enough...

if you're building your own circuits, then 2 channels I personally find limiting. but that's because of the work that I'm doing...

I like to build amplifiers and effects pedals for guitars, so I like to see my input wave, and my output wave, that's 2 channels, but with those 2 channels used up I'm not seeing any intermediate waves. if you're in college then that's fine, as you just grab a scope off the next desk, but I don't have stacks and stacks of scopes at home...

having said that... 4 channels is very expensive, so I do question if it's worth the extra money to have 4 channels when I could just change the way I'm working.

what you really need to think about is...
what kind of projects are you working on, analogue vs. digital.
what sort of frequency the signals you'll be analysing will be, (no good trying to analyse microwave frequency analogue signals with a really low frequency scope).
how many channels will you realistically need? (how many would be nice, vs. how many you really need like my example above, it's nice to see everything at once, but is it really worth paying hundreds more for something that's just nice when you can just look at things individually). -also when you consider old analogue scopes are cheap on ebay if you really need 4 channels you could get 2 or more cheaper 2 channel scopes rather than a 4 channel scope, for less money as well.

if you're buying analogue, check to see if the scope is calibrated, but realise that the calibration will probably be lost in transit anyway.

if buying digital, look for resolution, storage facilities, size of memory, USB expansion for more memory. the ability to plug in a printer even to print out traces.

if you're buying from ebay, make sure you don't buy a dinosaur, and make sure you see a picture of it working!
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