A thermometer is used at several stages in the brewing process to monitor the temperature of the mash, wort and even finished beer. The most popular thermometer for brewing is a simple floating thermometer which has a temperature range of 0-100 C, and is typically marked in both Farhenheit and Centigrade scales. When purchasing a thermometer, be sure to get one that has a range that at least spans from room temperature to boiling. Some more advanced brewing systems incorporate electronic thermometers which have a probe and separate digital readout.
Thermometers are used in the mashing process to monitor mash temperature during conversion, during the boil to monitor progress towards boiling, during cooling to determine when it is safe to add yeast, and during fermentation and aging to monitor fermentation temperature and conditioning temperature.