Abstract: A sensor means is proposed to determine an interior humidity and/or an interior volume delimited by a wall, in particular, of a vehicle passenger compartment 3, and a fogging up tendency of an inner surface of the wall, in particular, of a window 5 of the vehicle passenger compartment 3, with a dew point sensor 10 having a humidity sensor element 1 and a temperature sensor 2, wherein the humidity sensor element 1 and the temperature sensor 2 a thermally coupled, and a surface temperature sensor 4, wherein the dew point sensor 10 is designed to measure the air humidity and the room temperature of the interior volume and the surface temperature sensor 4 is designed to measure the temperature of the inner surface.