Hello, I have a question on you guys. I want to measure a negative voltage with my arduino. I found one circuit on the internet and I simulated the circuit in Microcap to find values of resistors, which would be suitable for my project.
Here it is: Circuit
It works fine, I measured some voltage levels with my multimeter and then I made a graph in excel to see if it measures correctly - see Graph. On the y axis are measured analog values and on the x axis is voltage.
But the problem is that I can’t figure out a way how to calculate the right values of the voltage from the measured values. I would be grateful for any advice…