. The Bell System technical journal . m n^. Changes in thefrequency arising from the changes in capacity C\ alter the energypicked up by the wave-meter circuit and this energy, which is recordedby means of a galvanometer, serves as a measure of the change ofcapacity or motion of the rod R. With this arrangement it is possibleto measure motions as small as 1 X 10^ cm. and under the best con-ditions as small as 1 X 10~^ cm. It is necessary to have good damping,which is obtained by means of immersing the drum D in polymerizedcastor oil. The accessory spring ^2 is used merely for calibratingpurpos
. The Bell System technical journal . m n^. Changes in thefrequency arising from the changes in capacity C\ alter the energypicked up by the wave-meter circuit and this energy, which is recordedby means of a galvanometer, serves as a measure of the change ofcapacity or motion of the rod R. With this arrangement it is possibleto measure motions as small as 1 X 10^ cm. and under the best con-ditions as small as 1 X 10~^ cm. It is necessary to have good damping,which is obtained by means of immersing the drum D in polymerizedcastor oil. The accessory spring ^2 is used merely for calibratingpurposes. Figure 18 shows the appearance of the apparatus as set up formeasurement. The condenser is contained in the lower housing atthe left, the wave-meter in the upper housing. The whole apparatusincluding the galvanometer is supported on a delicate spring suspensionwithin a second large lead container, the frame of which just appearsat the edge of the photograph and which is also supported by springs. 182 BELL SYSTEM TECHNICAL JOURNAL. THE CARBON MICROPHONE 183 Figure 19 shows the appearance of the complete setup with thecover on the outside container. This begins to compete with cosmicray apparatus from the point of view of the amount of lead involved,the outer container weighing about 600 lbs. Port-holes—one of
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
