Protecting a comparator in a tension measurement device
I would suggest clamp diodes, a DC blocking cap, and a series resistor.  The clamp diodes would be connected between the input pin of the comparator and both voltage rails, this prevents the voltage on the input pin from exceeding the voltage on the power rails.  Then add a series resistor to limit the current that can flow through the diodes when the voltage tries to exceed the rails.  Then you should add a parallel resistor to the comparator reference voltage.  Then add a decently sized DC blocking cap.  The idea is to get the oscillation centered around the comparator reference voltage so it will trigger nicely on the edges.  Size the resistors so they don't attenuate the signal too much, but provide a decent current limit.  Size the capacitor so it will not reduce the bandwidth below what you're trying to measure.