Hi Everyone, I've read a few different posts on how to read -5V using a voltage divider. Or even using an inverting op amp with gain of 1 to be able to read -12V at the input. I have tried setting up an inverting rail to rail op amp. However, my dual power supply reads -12V and positive 11.8V. So at the output I only read 11.8 instead of 12 when the input is -12.
Is there a better way to do this? Any other ideas I could try?
The project is that I have a monitor setup and as I vary the power the monitor output varies from -12V to -9.5V. I would like to have that monitor go into the arduino.