This sounds like a stupid question, but I can't find an answer anywhere. I realize that a lower filter freq on an analog input channel results in more smoothing, less noise, and less accurate representation of the signal, but my question is this: Is there any correlation between the filter frequency and the mains noise you might expect to be present. In other words, would you necessarily set a 50hz filter if you have 50hz power in the area, and a 60hz filter freq for 60hz supply power?