After the product had arrived with me, I have it adjusted in accordance with instructions - simply by I have it wrapped in a wet cloth and the pointer position have corrected after a short time to about 95%. Since then, the instrument fulfills his service - especially him coming with us to the good readability Good. It helps me to minimize the ventilation cycles in winter and still have a sufficiently dry air in the room.
Maybe I need a second instrument, in this case it will be this product again.