. An elementary manual of radiotelegraphy and radiotelephony for students and operators . One junction ofthe small suspended thermo-couple rests just above thestrip, but not quite touchingit, and is therefore heated byradiation and convection. Thecouple is therefore traversedby a current and deflectedin the magnetic field. Thisthermal detector is also quantitative. The complete instrumentis shown in Fig. 14. (4) We may detect the heating of the bolometer wire by itsown expansion, as first done in 1889 by W. G. Gregory. Thisarrangement is more suitable for detecting large and powerfuloscillatio
. An elementary manual of radiotelegraphy and radiotelephony for students and operators . One junction ofthe small suspended thermo-couple rests just above thestrip, but not quite touchingit, and is therefore heated byradiation and convection. Thecouple is therefore traversedby a current and deflectedin the magnetic field. Thisthermal detector is also quantitative. The complete instrumentis shown in Fig. 14. (4) We may detect the heating of the bolometer wire by itsown expansion, as first done in 1889 by W. G. Gregory. Thisarrangement is more suitable for detecting large and powerfuloscillations than feeble ones. The author has devised and useda hot wire ammeter made as shown in Fig. 1, Chapter VIII.,where the oscillations are passed through a fine wire, the endsof which are fixed. The expansion of the wire therefore producesa sag of the middle part, which is magnified by an index needleor by the movement of a mirror and a ray of light. The advantageof enclosing the bolometer in a vacuum is very considerable,because in the case of fine wires heated by a current the removal. {Reproduced by permission of the CambridgeScientific Instrument Company. Fig. 14. OSCILLATION DETECIOliS ?i5 of the lnut is chielly fffocteil l»y air conv»clioii, ami if iLt r» f«irowe stop this i-oiiveLtion by riiaoviii^ the air, tlio UjiniHTaturo oftho wirti rist*? higher for a j^ivcn iiitt^^ral efToet of the oscillatioiu. These iherinal diloctora are very useful for (juantitative workin the laboratory, because thoy can be so easily calibrated byjnussini; thruuj^li them a continuous current, and they are thereforenot merely ostillition detectors but are measurers of tlu^ intej^lvalue of the oscilliilions or of tiieir meati-sciuare value. Moreover,the thermal detcctore ai-o esj>ecially valuable in connection withtho mcjvsurement of undamped oscillations, as there we have todo with integral values which are large compared wiili tho integralvalues of damjwd oscillations. Another form of the
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1916
