I want to measure -30Vdc up to 0Vdc using a microcontroller. I'm basically measuring a voltage source with an output current of upto 2A.
I need to bring the voltage up onto a scale of 0V to 5V so that I can use the ADC of my microcontroller. I found two types of solutions to do this.
One with a simple resistive adder as shown below:
and another with a non inverting summing amplifier:
What I need help with is that I don't understand the specifications for this offset voltage source? Can I use a resistive divider circuit on my 5V power rail to provide this voltage? How do I calculate the current to be provided from this offset voltage source so as to create the divider?