I find if I worry about it, I make it worse. I don't even have a thing that reads it. My bator has two wells. You keep one filled the entire time. The other you fill also on the last three days. I always have good hatch rates. And It saves stress. I congradulate the people who keep track of it, and keep it steady and stuff. But if I did that I would fret about it all the time. I turn 3 times a day, and keep the well full. Then 21 days later I have chicks.