LCD 16x2 showing strange

to liudr:
I have only cheap voltmeter, so I cant measure it precisely. I have only one... I dont know what you mean by interchangeability, look at datasheet. Is there some more accurate solution to measure temperature, like using LM35 or digital DS18B20?

my altitude is 570mas check it here http://mapy.cz/s/3zQq

kty81_1.pdf (93 KB)