I am trying to read quite low amps with arduion, using the shunt resistor. The problem is the amps are so small i get zeros on analog pins, so i am trying to amplify it with LM358 Amplifier Module (www.openimpulse.com/lm358-amplifier-module
I have very simple circit now, just to try to find out how exacly it works. (Circuit attached).
If the module is not connected to the resistor, the arduino says something about 510 (+-10) which is half of the power source on the amp and that should be okay from what i understand.
But when i connect it to the resistor it shows these values (first is voltage on source, second is on the OUT of the amplifier):
The "amplified" values seems to be totaly indifferent to the source voltage or screwing the pot. And that makes absolutly no sense to me.
I would be very glad for any advice or tip how to solve this problem, or other way how to simply measure low amps with arduino. ¨
Additional info: The source is a sollar cell and i am trying to make a apparatus to measure its IV characteristics so in the end there will be additional potentiometer in the circuit.