I'd like some help understanding this previous thread about a current transformer input to ADC. The part I don't understand is how the reference of the input circuit is tied to the reference of my ADC. It seems to me like the rectified AC input needs to somehow share the same reference as the one being used by my ADC in order to get a consistently accurate reading. I can't quite figure out how to do this while protecting my MCU from the negative of the AC signal. Any help would be greatly appreciated.
Here are the requirements for my system, if it matters at all: The MCU is powered by a truck battery at 9-32 Vdc. This part of my system is required to measure the current provided by a generator, which can be 50-400Hz, 120 or 240 VAC, up to 400A. My system is provided a signal from the secondary of a 150:5A current transformer, which I must use to measure the current with an accuracy of 1%.