BOLOMETERS. 



167 



Table VII. Bolometer-Galvanometer Sensitiveness. 



Temperature sensitiveness. 



For 1 mm. de- 

 flection and 

 period given 

 in col. 3. 



C. 

 1X10- 6 



9X10- 6 



8X10- 



3X10- 



2X10- 4 

 5X10- 6 



r Ibid., 

 for a scale 

 at 1 m. 



2.5X10- 



Ibid., for 



a scale at 1 m 



and a full 



period of 



15 sees. 



C. 



4X10- 



Candle test. 



a "2 

 2 ? 



met. 



u S 



c o 



m a 



tn g 



bo 



met. 



-a a 

 o> o 



S J 



o-S 



800 



60 



. -A u 



<V CZ2. 



?^ 



> c>2 



IrS *. 



cry 4)" 



03 



Remarks. 



In practice for solar spectrum 

 work a full period of 3 sees, 

 and i=2.2Xio -9 ampere is 

 used. Balancing coils of plati- 

 noid. Bolometer is inclosed in 

 water jacket. 



In practice drifting is minim- 

 ized by placing a short copper 

 wire in series with one of the 

 bolometer arms. 



Surface bolometer; 23 strips of 

 tin foil; blackened with PtCl 2 

 and soot. Balancing coils of 

 copper wire in separate box. 

 Sensitiveness 556X10 -9 gr- 

 cals/cm 2 /sec. 



Single Pt. strip 0.1X12 mm. in 

 spectrobolometer. 



2 arms of tin foil in form of grat- 

 ing. Sensitiveness also given 

 as 127X10 -9 gr- cals/cm 2 sec. 



Bolometer strips of nickel 0.002 

 mm. thick. Balancing coils of 

 platinum wire in oil in sep- 

 arate box. Found deflection 

 proportional to current. 



Surface bolometer, 4 similar 

 arms, so no compensating re- 

 sistances needed; diagonally 

 opposite arms exposed. Sen- 

 sitiveness also given as 533 X 

 io -9 gr-cals/cm 2 /sec. 



Surface bolometer 4 similar 

 arms of platinum foil 0.001 

 mm. thick; 2 diagonally op- 

 posite arms exposed to radia- 

 tion surface consists of 1 2 strips 

 of platinum, 1 mm. wideX32 

 mm. long, separated by 1.5 

 mm., back of which openings 

 are 12 similar strips of the 

 diagonally opposite arm. Bo- 

 lometer currents as high as 

 0.04 ampere could be used. 



Surface bolometer of tin foil 0.01 

 mm. thick; 7 strips in each arm. 



2 arms of 0.04 mm. iron wire 

 hammered flat; 3 strips in 

 each arm. 



