I have a 10R0 resistor connected to +9V from a battery on one side and the other side is connected to a load that draws 0-100ma.
Since the voltage drop across this resistor would be 0-1V, I originally thought it would be no problem to measure it using the differential ADC on my Tiny84. Now I realize even though the differential is only 1V, I still need to drop the actual voltages below the 5V my Tiny is running at.
So, it would appear that I need a resistor divider network to drop the 9V on the high side of the sense resistor as well as a resistor divider on the low side 9V-8V.
Do these two divider networks need to be matched? Or is there another way to get this 1V differential into the ADC without the two divider networks?