thermometer/hygrometer question

[hoosiersphynx]

Ok I went and got one from Walmart today put it in the bator and it is reading 90.something when the glass one is reading around 99.5? What is wrong?
Thanks
Rebecca

 

[chicmom]

Maybe it needs a fresh battery?

 

[alicefelldown]

Did you calibrate it?

http://exoticpets.about.com/od/herpresources/ss/hygrometer.htm