Hi! I am trying to use MCP3421 in order to monitor Battery voltage. All are fine when i use external battery with no common wiring with the main sytem. The problem begins when i am measuring the system battery. Here is the diagram https://www.dropbox.com/s/an4kftyxp0iejyw/mcp3421-gauge.jpg?dl=0 Arduino does not run. Is there wiring problem?
I tried to power first the arduino and then connect battery contacts to ADC chip mcp3421 and it works fine. So why do i have to power arduino and theN connect battery to ADC Analog inputs?