I have two thermo/hygrometers in a big sandwich bag with a coffee cup 1/2 cup of salt 1/2 cup of water. The large one seems to be correct. It is from Radio Shack. The humdity goes from 74% to 76%. The smaller one that lots of people here seem to like - a small Springfield from Wal-Mart. Is only at 67%. What do I do now with the Springfiled? Can it be manualy calibrated or is it a dud? These have been in the bag for 36+ hours now. Advice anyone? I have eggs going in early next week.