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How can I measure the noise on my AC mains with a 2ch oscilloscope?

I’m not an EE so although I have some nice test equipment I need help. Here is the problem, the AC Mains are 120 vac but I’m trying to measure the noise on the AC signal , millivolts. I’d like to answer two questions how bad is my power and second  does my isolation transformer make a difference.

 

thanks for the help 

badbruno
jasonbourne71's avatar
jasonbourne71
1,183 posts
 

Your components' power supplies are designed to putput clean DC to activate the circuitry. No need to worry neurotically about noise on the AC line. Competent engineering takes care of that.

badbruno OP
35 posts
 

Thanks you sharing your insights and perspective. I never thought of this as being a Hack… hmm 

yes the AC into the OScope is an issue even with my 10x or 100x probs.

Can you share some leads to these “on line resources” ?

Hey OP? 

thanks 

 

badbruno OP
35 posts
 

Jason you make a good point !

Post removed 
carlsbad2's avatar
carlsbad2
1,616 posts
 

OP.  While that is a nice experiment, it isn't really necessary.  Nobdy has good quality power coming into their home today.  Too many non-synchronous loads on the line that mangle the sine wave.  My power generally runs 4% thd or so.  

I don't have a stand along o-scope.  My PSA P10 has a built in scope with fixed settings to measure it.  Here is a random graph:

 

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