I am designing a PCB with a PIC 16 microcontroller. The purpose of the PCB is to measure the voltage of a button cell battery, before the battery is placed in its device (assume this battery testing is involved in a mass production line, so its used very much, and very quick). Now I am using a sort of clothspin to clamp the battery on the top and bottom side (anode and cathode). But the mistake to reverse the polarity of the battery is very easy to make. For that reason I want to include a reverse polarity protection, so that if the battery is placed wrong (negative voltage on the analog input) it doesn't fry my microcontroller. What is the best option I can use? A diode won't do the trick in my opinion since that makes the voltage that I want to read drop, but I also don't want to make a very difficult circuit for this RPP.
This is the circuit. The Battery wire is going to the analog INPUT. The resistor values are not right yet. They will be something like 100, 1000, 1000 ohm.