Rodrigo wrote:
>Hi all,
>
>After reading the benefit of an oscilloscope, i took one that is not used in
>my work to debug (is this used in hardware too ?) a pic circuit. I have ZERO
>experience with scopes, so, and i attach the probe to Ch1, the probe has a
>clip, i grip it to gnd and the pin of the probe to what was i really want to
>measure... BUT, i have a 50Hz superimposed over my signal, and showme not
>really what i expect, then measuring the line ac make some spark in the
>probe (the scope can accept 400 vac). Using a tester, and the scope off, i
>discover that the clip is connected to the line ground (0 ohm), and i
>suppose that the test probe was isolated from the main line. I'm wrong and i
>must go to buy "measuring with a scope for newbies" or the scope is bad?, i
>don't have none to ask in my work, because is not used and is there only by
>a mistake

Ouch !  Yes, it's normal for the CRO probe to be referenced to mains earth.
If you want to measure points at mains potential you will need to use a
isolated probe adapter or similar. The scope and/or the probes may have
been damaged now. I'm not familiar with your 'scope. Measuring mains
without the appropriate probes/adapters can be tricky & quite dangerous.
Regards...

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