There are basically two methods to process AC (current or voltage) measurements.
- Use a precision rectifier (producing average rectified value), RMS detector or peak detector circuit, depending on the measurement purpose. Read its output with ADC. Circuit filter time constants have to be dimensioned according to AC frequency, accuracy and response time requirements
- Read the instantaneous value with ADC, generate average rectified, RMS or peak measurement in software. ADC rate must allow sufficient oversampling of the AC signal.