. Instruments and methods used in radiometry . Thermopile. (May 24, 07; Nernst heater on 98 volts at 1 m. frombolometer. Galvanometer (full) period8 seconds undamped; 50 ohms in deflection about 80 cm. Bolom-eter is perfectly steady, and comesto rest abruptly. Readings vary to per cent from mean of about10 in each set. Temperature sensi-tiveness— 6° Conditions are the same as for the bo-lometer. Thermopile deflectionscreeps, and does not come forestin the same time as the galvanometer(on open circuit or with the bolometer),due to its
. Instruments and methods used in radiometry . Thermopile. (May 24, 07; Nernst heater on 98 volts at 1 m. frombolometer. Galvanometer (full) period8 seconds undamped; 50 ohms in deflection about 80 cm. Bolom-eter is perfectly steady, and comesto rest abruptly. Readings vary to per cent from mean of about10 in each set. Temperature sensi-tiveness— 6° Conditions are the same as for the bo-lometer. Thermopile deflectionscreeps, and does not come forestin the same time as the galvanometer(on open circuit or with the bolometer),due to its larger heat capacity. Gal-vanometer single swing of 4 seconds isincreased to 6 seconds and is fullydamped due to lag of thermopile; 50ohms in series with sensitiveness=2° X10-5. Source and disk nearer the screen. Dif-ficult to read the deflection on accountof the creeping, which amounts to 1to 3 mm. Readings made at end of 6seconds vary by per cent from mean;20 ohms in series with the galvanom-eter. Temperature sensitiveness=5°X10-6. The thermopile of wire (20 junctions covered with a mm wide), already described, showed a slight lag in registeringthe energy received. Although this was not marked, there was a 450 Bulletin of the Bureau of Standards. [ tendency for the deflection to creep instead of stopping abruptly,as in the ease of the bolometer
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