To be able to measure the value with an Arduino Nano I want to convert the negative rail voltage to positive. I tried to build a simple inverting amplifier with unity gain using LM324. The supply is +/- 10V.
The voltage is converted but scaled down. When I measure the voltages on the pins I see the values noted in below pic with red. It seems that the inverting pin can't be pulled to pin non-inverting pin value.
For the test purposes I didn't attach any output load to the circuit.