If your oven is older it may not be maintaining a constant temp. Mine was this way and I looked at a variety of gadgets to measure the temp. I finally settled on this kitchen aid thermometer. For the first few months it was spot on in telling e temperature but after about a years use I measured the oven using a thermal meter and my thermometer was about 7 degrees off, still closer then my stove said it was. Overall I'm happy with this and would buy it again.