So you have a sinusoidal signal between 2 and 7 volts. You decide to use a comparator with what looks like a bogus voltage reference (Try instead a voltage divider of two resistors between VCC and GND, with the quota 4/9), and then you feed your comparator with 9V.

Without looking at the datasheet for your specific comparator - do you expect your comparator to produce 0 and 5V suitable for your processor (or possible 0 and 3.3V if you have a 3.3V processor)?

And why do you use a sensor construct that gives 7V in the first place? You have not made any post describing that the 7V part is outside your control so why not fix the problem at the root, instead of spending time adding bandages?