My sensor gives output between -10V and +10V. Then I decided to use a simple voltage divider circuit to be compatible with the ADC input range. I used a power supply like the sensor, the expected output voltage should be about -2V at the input of the ADC.
But although increasing input voltage up to 20V the voltage stays the same as -0.7V.
Then I use LM741 OPAMP as a buffer, but the result hasn't changed.
Still, about -0.7V is seen.
Why I'm getting such results and the voltage divider doesn't work?