I am trying to send an AC signal into a microcontroller. I have to first scale the signal to the appropriate voltage, and then send it through an ADC so that my microcontroller can use it. The other option is to scale and offset it, and send it straight into the controller. Here is a picture of the two circuits.

** NOTE: The box on the second circuit denotes the circuitry to scale and offset. The second circuit does not require an ADC as drawn. I would send the 0-3.3V signal straight into the microcontroller and use the internal ADC.

Question: Is there an advantage to using either one?

 

Using the internal ADC of the uC is obviously cost effective.
LTC2328 is 18 bit, 1 Megasamples ADC and I am not sure whether you get that kind of speed and resolution with integrated ADCs in uC. So it would depend on the speed and resolution that your application requires.

 

i would use a full wave bridge and half the signal with resistors..

https://mlabsbd.files.wordpress.com/2013/11/adc1.png