Re: Are low/lower cost USB Oscilloscope's any good?

news.valornet.com wrote:
Hi,

I am just trying to mess around with electronics stuff, and I don't know too
much, but I've put a circuit or two together with help from this forum and
others. I've got a fluke DMM and clampmeter, but I'd really like to be able
to scope some stuff sometimes. I just don't know if I could part with the
money for a portable scope like a fluke 123 however just for playing around.
I have some questions and appreciate any suggestions for what might be good:

What you want for starters is a proper analog scope. A 20MHz dual trace
model is a basic starting point, or even the 10MHz single channel Phil
pointed out.
You can get cheap 2nd hand scopes on eBay and surplus gear sellers.

1. Do most scopes have decent voltage input on them? For example, can you
hook most of them up to line power (120vac or 240vac)? I am assuming the
fluke can do this no sweat, but I don't know.

DON'T muck around with probing the mains unless you know exactly what
you are doing.
If you want to do it *safely* you need a proper high voltage
differential isolating probe, and these are not cheap.

2. I also see a bunch of references to X10 probes. Are these used to
reduce the voltage to something a scope can use, for example 240VAC -->
24VAC ?

x10 probes are used for probing higher speed signals. In most normal
cases you would use a x10 probe.

3. Do you have any recommendations for a scope that works on a notebook
that is relatively low cost that has decent features (keep in mind I have no
idea what features you would want in a scope).

If you want to capture weaveform (for example, analysing a serial
digital signal) then you need either a digital stoage scope (DSO), or a
PC based one. In any case, you should get a real analog oscilloscope as
well for general purpose use.

With DSO's, memory depth and sample rate are the top two requirements.
The more the better.

I would even consider some of these scopes that are free based ones that
work with a sound card, but my question is, what type of voltage input can
you get with a microphone jack???

If you really want to work on high voltage gear, you MUST get a proper
differential probe. Anything else mixed with lack of experience will
either kill you or your equipment.

Dave :)

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