ABSTRACT
The thermocouple was discovered in 1821 by the Russian-born German physicist, J. Seebeck [1]. He discovered that at the junction of two dissimilar conductors, a voltage could be generated by a change in temperature (see Figure 7.1). Using this effect, Melloni produced the first bismuth–copper thermocouple detector in 1833 [2], to investigate the infrared spectrum. The small output voltage of thermocouples, of the order of some μV/K for metal thermocouples, prevented the measurements of very small temperature differences. Connecting several thermocouples in series, first carried out by Nobili in 1829, generated a higher and therefore measurable voltage.
