A new instrument for infrared radiation measurements: the thermopile of Macedonio Melloni

Summary

Towards the second decade of the nineteenth century Seebeck discovered that when two different conductors are joined together at both ends with the two junctions kept at different temperatures, an electromotive force arises. Seebeck's discovery, thanks to Melloni, converted the thermopile into the best measuring apparatus for the study of radiation. In this paper I discuss some technical properties of the thermopile used by Melloni in his early studies on radiant heat polarization; quantify in modern terms the behaviour of the thermopile; and solve an enigma concerning its sensitivity.