For these two points, the current is varied but the position is maintained constant. Thus the temperature change caused by a slight change in current is determined. With each temperature versus position point, the current flow is also measured. At the conclusion of the profile determinations, the average current is calculated and the individual temperature data are corrected to what the temperature would be if the average current had been flowing when the temperature measurement was taken. The thermal conductivity and Thomson coefficient are calculated using Eq.
T is usually and adequate representation.
After the conductivity values have been determined over one temperature interval, profile data at higher temperatures are obtained and the process repeated. Additional long sample data are taken in between some profile determinations to determine any changes in the emissivity and resistivity. Typical thermal conductivity results are given in Figure 15.