In order to use Seebeck effect to measure temperature, thermocouples have been developed. Two types of metal are connected, one for the hot end contact and the other for the reference end contact (output terminal side). If the temperatures of the two * are made different, a thermoelectric motive force with a constant relationship to the temperature difference is produced. Here, if you hold the reference end at a constant temperature, you will know the temperature of the hot end.