smoothing an level shifted AC signal - Good or Bad

Question

I have ac Signal fed into an arduino ADC. Some say sampling is better than smoothing the signal. Why is that ? Circuit is as shown below.

dougw · Answer

If you want to know the amplitude of the AC, you should rectify it before filtering. if you just filter AC you get the average value, which is always zero.

dougw · Answer

Put a diode in series with the AC signal before any filtering.

If you need to see small voltages, reference the other side of the AC signal to a .7 V voltage divider. (to overcome the diode voltage deadband) This makes the signal start at .7 V but there is no deadband.