Low analog lowpass + ADC vs High analog lowpass + ADC + low digital lowpass I'm doing EEG data collection and my amp forces use of an analog lowpass filter before the ADC. I'm fairly sure that I won't be interested in phenomena associated with frequencies of 30Hz or higher, so it strikes me that the most disk-space efficient thing to do is to analog lowpass at 30Hz (it uses a Bessel filter) and tell the ADC to sample at 60Hz. However, disk space considerations aside, I'm curious whether there is any difference between this strategy and, say, setting the lowpass to something really high like 250Hz and sampling at 500Hz, then once digitized and doing analysis, applying a digital lowpass at 30Hz. Would the double filtering induce artifacts? (i.e. Should I opt for the low analog lowpass for reasons other than disk space?)
I'm curious whether there is any difference between this strategy and, say, setting the lowpass to something really high like 250Hz and sampling at 500Hz, then once digitized and doing analysis, applying a digital lowpass at 30Hz


Good idea.  This is how oversampling ADCs work, sampling at a high rate using a poor quality converter (even a 1-bit converter), and then using digital filtering to downsample to the desired value with better accuracy.  Digital filters can have a much sharper cutoff than analog filters for essentially no cost, reducing aliasing that would otherwise get into your recording.  It can also improve your signal-to-noise if the analog signal isn't already restricting this.


  Would the double filtering induce artifacts? 


Not unless you design the filters poorly.  :)