AC current sensing using micro-controller and suitable circuit
If you have two ADC channels avalable you could run a scheme like this: 







simulate this circuit &ndash; Schematic created using CircuitLab

This avoids switching and allows you to have options on your dynamic range.  

If you only have one ADC channel you can get an analog mux and use it to select between the low and high gain and that way you don't have to do anything to your sensitive current signal.