What is the purpose of connecting the resistance of 2.2 M ohm with the analog input signal as shown in the diagram

[Pawa111018]

 

[Bluejets]

Possibly a pullup resistor for an open collector on the sensor.

 

[Delta Prime]

Can you show the entire schematic. And what is the application please.
looks to me like they are trying to add external hysteresis to a comparator, having high and low trip points.

 

[Bluejets]

Fairly certain that is what I already said.........