I am getting 27%RH at 21 Celsius -dry but ok.. but when i increase temperature to 40 degrees of Celsius i get result 4% RH ..
Sensor is in the sealed box with two ventilators..
...even if i put inside wet towel i still don't get more than 11% RH
do i have problem with sensor or with understanding the physics??
Physics. RH is a measure of how much water there is in the air compared to the maximum amount of water that the air can hold. The amount of water that air can hold increases with temperature. The tables at http://en.wikipedia.org/wiki/Vapour_pressure_of_water
describe how the saturation vapour pressure of water (i.e. how much water air can hold) varies with temperature, and from that you can work out whether a drop from 27% to 4% from 21C to 40C is reasonable.