common-mode noise measurement

Discussion in 'General Electronics Chat' started by bug13, Jun 8, 2016.

  1. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
    1,208
    38
    Hi guys

    How do I measure common-mode noise? The best I can find in the world wild web is this from TI.
    http://www.ti.com/lit/an/slla057/slla057.pdf

    I assume I can just hook a DUT and set the scope to AC couple as the scope is earth reference?
     
    Last edited: Jun 8, 2016
  2. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,886
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    On what are you measuring the common mode voltage?
    The whole point is that all earths are not equal. Quote from the pdf:
    The biggest source of common-mode noise is the difference in potential between two physically
    remote grounds.
     
    dl324 likes this.
  3. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
    1,208
    38
    I am just playing around, I tried to measure a SMPS (unplug), hook the outputs to a scope with AC coupling, X1 probes. After reading a lot of common mode noise, I just want to see it. It's something I want to do when I learn something new.
     
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