I'd like to measure the output voltage on a power supply with a ADC and a micro-controller. The ADC is powered from a different source and the grounds of the power supplies are not connected. How can safely I measure the differential output voltage of the power supply? I'm sorry if this is a standard question, but I can't find a simple solution.
Edit in response to the comments: The voltages I want to measure range between 0 and 14V. Precision is not important (a few percent). Frequency of measurements is low (about 1Hz). No high frequency components present.