common-mode noise measurement

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

  1. bug13

    Thread Starter Senior Member

    Feb 13, 2012
    1,257
    41
    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

    Distinguished Member

    Jun 4, 2014
    4,063
    931
    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 Senior Member

    Feb 13, 2012
    1,257
    41
    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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