@TolpuddleSartre:
I don't think it's that cold and dry where I am. A prove could be, that I'm sitting here with a t-shirt and I don't feel cold. 
@wvmarle:
I tryed print statements, too. But they're displaying zero, also. So this should not be the problem. BTW: How is it possible to see print statements with the Arduino IDE? As I know it doesn't have any debugging possibility.