Figure 17.3 Macedonio Melloni; Figure 17.4 Samuel - FLIR ThermaCAM P20 Operator's Manual

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Figure 17.3 Macedonio Melloni (1798–1854)
Thermometers, as radiation detectors, remained unchallenged until 1829, the
year Nobili invented the thermocouple. (Herschel's own thermometer could be
read to 0.2 °C (0.036 °F), and later models were able to be read to 0.05 °C (0.09 °F)).
Then a breakthrough occurred; Melloni connected a number of thermocouples
in series to form the first thermopile. The new device was at least 40 times as
sensitive as the best thermometer of the day for detecting heat radiation – capable
of detecting the heat from a person standing three meters away.
The first so-called 'heat-picture' became possible in 1840, the result of work by
Sir John Herschel, son of the discoverer of the infrared and a famous astronomer
in his own right. Based upon the differential evaporation of a thin film of oil when
exposed to a heat pattern focused upon it, the thermal image could be seen by
reflected light where the interference effects of the oil film made the image visible
to the eye. Sir John also managed to obtain a primitive record of the thermal image
on paper, which he called a 'thermograph'.
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Figure 17.4 Samuel P. Langley (1834–1906)
The improvement of infrared-detector sensitivity progressed slowly. Another
major breakthrough, made by Langley in 1880, was the invention of the bolometer.
This consisted of a thin blackened strip of platinum connected in one arm of a
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