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You don't want to have to wait several minutes while the thermometer determines the temperature, so choose an instant-read variety. Make sure it gets cleaned after each use. You should occasionally calibrate your thermometer to be sure it gives an accurate reading. To do so, fill a small pan with water and bring it to a rolling boil. Take the water's temperatureit should be 212F (100C). Turn the hex bolt at the bottom of an analog thermometer to calibrate the temperature if it is incorrect. Consult the manufacturer's directions to calibrate a digital thermometer. The edges may be warmer than the center, so to know if your cake is done, you'll need to test the temperature in the middle. Don't push the thermometer down to the bottom of the pan, simply stick it halfway through the cake. Keep in mind that sticking a thermometer in the cheesecake may cause it to crack, so try to only test the temperature once, rather than multiple times. If you must test it more than once, stick the thermometer in the same hole you used the first time to minimize cracking. Once the center of the cheesecake reaches 150F (66C), the cake is done! Take it out of the oven and allow it to cool completely on a wire rack. If it is not yet done, put it back in the oven for about 5 minutes, then check it again to see if it is done. Repeat until you get a reading of 150F (66C).
Obtain an instant-read cooking thermometer. Test the temperature in the middle of the cake. Look for a reading of 150F (66C).