[sdiy] Scope Probe

[Eric Brombaugh]

In general a scope will work just fine without probes. You may need to 
be careful how you interpret the Y axis scale, depending on if it's set 
up for 10x or 1x probes, and you should also be careful if the scope 
inputs are 50 ohm or 1 Meg-ohm impedance - that can affect the way the 
scope loads the circuit you're looking at, as well as the scale.

I assume that "but that wave like the smaller part of a bigger wave" 
means either:
a) your /\/\/\ signal seems superimposed on a larger, lower frequency 
wave. This is what you might see if the scope and the signal generator 
aren't sharing a common ground. The larger wave would be a 60 cycle hum. 
Make sure the scope is grounded to your signal generator

or b) the /\/\/ signal has it's tops/bottoms chopped off - just change 
the Y axis scale until you can see the whole thing.

Either way, it sounds like your scope is working. If so, a decent set of 
probes would be a good investment. They will help you get into tight 
spaces, they reduce the load the scope presents to your circuit and they 
are more convenient than shoving a bunch of bare wire into the BNC 
connectors and hoping they stay.

Eric

Jim Bob wrote:
> Sorry for the totally beginner question.......
> Ive got an old scope that I got for free, w/ no probles.  Ive tried 
> using it w/out the probes.  Just using wires.  Should it work at all 
> like this?  I can get it tuned in to a wave /\/\/\/  but that wave 
> like the smaller part of a bigger wave that goes up and down the 
> screen.  Ive tested several things and all seem to have the same result.
>
> Is this thing broken, or will it work if I get a probe?
>
> thanks
>
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