MCC 118 ground/reference for automotive data logging

[JamesK]

I have found that the "AGND" pins of the MCC 118 are connected to the GND pins (V-) on the raspberry pi 3. Suppose I want to log an automotive battery voltage (voltage into an ECU) - if the raspberry pi is powered from a different source (eg, USB Power Bank) will I run into issues with the different grounds? Am I attempting something silly?

I could also possibly power the R Pi + MCC118 off the automotive bus, but there are applications where it would be much easier to have a dedicated external power supply.

[Fausto]

Hello @JamesK.

Your wiring diagram will create a ground loop as is.

One possible solution that I found searching the internet may be to use a USB Digital Isolator between the RPi and USB Power pack.

Regards,

Fausto