You all may think I am paranoid but I use 3 thermometers in my incubator. I have a digital reptile thermometer with a probe which I can hang at the middle of the bator near egg tops, a regular old glass incubaor thermometer (Not accurate, but just for extra backup) and a digital reptile thermometer/hygrometer combo that I got at petco. I check all of them and don't depend on the readings from a single device.