bolometer

bo·lom·e·ter   (bō-lŏm'ĭ-tər)    n.  An instrument that measures radiant energy by correlating the radiation-induced change in electrical resistance of a blackened metal foil with the amount of radiation absorbed. [Greek bolē, ray; see gwelə- in Indo-European roots + -meter.] bo'lo·met'ric (bō'lə-mět'rĭk) adj., bo'lo·met'ri·cal·ly adv.

Main Entry: bo·lom·e·ter
Pronunciation: bO-'läm-&t-&r
Function: noun
: a very sensitive thermometer used in the detectionand measurement of feeble thermal radiation and especially adapted to the study of infrared spectra —bo·lo·met·ric /"bO-l&-'me-trik/ adjective —bo·lo·met·ri·cal·ly /-tri-k(&-)lE/ adverb

bolometer

instrument for measuring radiation by means of the rise in temperature of a blackened metal strip in one of the arms of a resistance bridge. In the first bolometer, invented by the American scientist Samuel P. Langley in 1880, a Wheatstone bridge was used along with a galvanometer that produced a deflection proportional to the intensity of radiation for small deflections. A later bolometer consists of four platinum gratings (each of which is made of a series of strips) inserted in the arms of a resistance bridge; two of these gratings, in opposite arms of the bridge, are placed one behind another, so that the openings of one are opposite the strips of the other and are exposed to the radiation, the other opposite pair being shielded; this arrangement doubles the effect on the galvanometer and also compensates for any extraneous temperature changes. Changes in temperature as small as 0.0001 C may be detected in this way

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