A measuring device for detecting a humidity and temperature of a window surface including at least one moisture sensor and at least one temperature sensor placed on the window surface, an evaluation unit connected downstream from the moisture and temperature sensors, and a signal converting and linking unit placed between the moisture and temperature sensors and the evaluation unit. Further, when the temperature sensor detects a change in a temperature of the window surface or the moisture sensor detects a change in a moisture of the window surface, a frequency of an oscillator included in the signal and converting unit is changed.