. Instruments and methods used in radiometry - II . to a source of radiation. The variouscurves represent different gas pressures. In this experiment thebolometer was mm wide. Using a bolometer mm widethe curves see Fig. 11 do not come to such a sharp maximum asthe ones shown in Fig. 9. :: Wait org Leithauser, and Johansen: Ann. derPhys., -4, p. 25; 1907. u Buch.~ali: .A, cer p-y;. _ 00. :. ,;:: :::;. Cobientz] Instruments and Methods of Radiometry 2. THE CONSTRUCTION OF SENSITIVE BOLOMETERS 37 In the bolometer the sensitiveness is closely proportional to thesquare root of the surface
. Instruments and methods used in radiometry - II . to a source of radiation. The variouscurves represent different gas pressures. In this experiment thebolometer was mm wide. Using a bolometer mm widethe curves see Fig. 11 do not come to such a sharp maximum asthe ones shown in Fig. 9. :: Wait org Leithauser, and Johansen: Ann. derPhys., -4, p. 25; 1907. u Buch.~ali: .A, cer p-y;. _ 00. :. ,;:: :::;. Cobientz] Instruments and Methods of Radiometry 2. THE CONSTRUCTION OF SENSITIVE BOLOMETERS 37 In the bolometer the sensitiveness is closely proportional to thesquare root of the surface, so that in spectral energy work, wherethe bolometer strip is narrow, the sensitiveness attainable throughthe bolometer is limited. Since writing the previous paper the present instrument hasbeen considerably changed, and the experience gained indicatesthat in air bolometers it is not advisable to use platinum which ismuch less than mm in thickness. The methods of mountingare as before described. In mounting the bolometer strips on the 200. ,1 amp. holder, the one exposed to radiation is first soldered in place,using rosin for a flux. The unexposed strip is made a little longer,so that it will have a slightly greater resistance, which by subse-quent resoldering is made equal ro that of the exposed strip. Thisis a difficult task when using very thin bolometer platinum. Inone of the latest bolometers (No. 9; mm thickness) con-sisting of platinum strips 10 by mm, the resistance of the exposedstrip is ohms and of the unexposed strip is the risk of breaking is too great to balance to such a nicety 38 Bulletin of the Bureau of Standards [VoUg and in the vacuum bolometer, known as Xo. 10, to be describedpresently, the bolometer strips are balanced to i per cent. The question of a satisfactory slide wire for balancing thebolometer has required considerable attention. It was found thatthe const ant an slide wire became soiled and required frequentp
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