Hi Spec, included is a concept drawing for the current and voltage measurement. Since I hang the controller (Atmega Pro Mini 16M 5V) from the positive side, its ground hangs 5 V lower, yet 44Vdc (rectifier bridge output) - 5Vdc = 39Vdc above the PSU ground. The PSU regulates between 0Vdc and 30Vdc, therefor the voltage feedback to the controller is between -39Vdc + 0Vdc = -39Vdc and -39Vdc + 30Vdc = -9Vdc. So I need to convert voltages between -39Vdc and -9Vdc to 0Vdc and +5Vdc.
For the current measurement I insert the INA219 in the positive supply line. Powering the INA 219 is straight from the controller supply (over the Zener, 5Vdc).