RMS Amplitudes of voltage
RMS includes the mean. If you want a metric for &quot;variation&quot; use the standard deviation instead or subtract the mean first (which is basically the same thing).
For the black curves moves slowly, but it still moves by a good amount. If you want a metric of the &quot;fuzziness&quot; than you can apply a high pass filter first that gets rid of the slow &quot;drift&quot; movemenent.