According to the Seebeck effect, a voltage measured at the cold junction is proportional to the difference in temperature between the hot junction and the cold junction. This voltage may be referred to as the Seebeck voltage, thermoelectric voltage, or thermoelectric EMF. As the temperature rise at the hot junction, the observed voltage at the cold junction also increase non-linearly with the rising temperature. The linearity of the temperature voltage relationship depends on the combination of metals used to make the thermocouple.