DEVICE FOR EVAPORATING A FLUID THAT IS ABSORBED BY A POROUS SUBSTRATE, AND METHOD OF ESTIMATING A LEVEL OF FLUID THAT IS ABSORBED BY A POROUS SUBSTRATE
Method of estimating a level of fluid that is absorbed by a porous substrate, wherein fluid is absorbed by the substrate, wherein a light is arranged near the substrate such that it emits light rays directed to the substrate, wherein the light intensity of the light rays transmitted through the substrate changes under influence of the decrease of the amount of fluid that is absorbed by the substrate.