My concerne is about the selected circuit in RED
I did not understand how does this ciruict works! *Why have we used R24=1.2M? Especially in case we remove R21 (As it is noted by DNP)
*What is the contribution of R16, C12 and R18 in measuring the current flowing through a parallel resistors R4 and R5
*What about C15, is it used as a filter or just for optimization?