If you download the OS3.0 main controller EagleCAD files:
https://github.com/OpenSprinkler/OpenSprinkler-Hardware/tree/master/OS/3.0/Master
and open the .sch in EagleCAD, you will see a section that looks like below. That’s the precision rectifier circuit. What it does is to rectify the AC voltage that falls on the 0.2ohm current sensing resistor to DC voltage, then feed that to an ADC pin.
