I use this one also - in fact bought 2 - one for the hatchout area and one for the incubator area of the cabinet....Very helpful and consistently reliable...I was greatly impressed!
That is the one I have that I cannot trust. It gives weird readings all the time, never reads higher than 20% humidity. I do have a little silver Springfield that used to be good on temp, then it began reading 2 degrees low and now, the hygro doesnt seem to work well, either. Getting good and really reliable, accurate instruments is the hardest part of incubating!
Mine gave me some weird readings too. Finally, I was using it as a brooder thermometer and bumped the heat lamp and melted it. I use a Fluker's hygrometer that I bought from PetCo that works really well.