Abstract
The vacuum thermocouples herein described had a sensitivity of about 1μV for 10−8 Cal. sec−1 falling on a receiver 0.5 mm2 in area and reached practical thermal equilibrium in 0.1 sec. The sensitivity in vacuum was usually 20 to 40 times the sensitivity in air. Very short fine wires of high thermoelectric power, bismuth alloys, were soldered to a gold leaf receiver which was blackened on one side by electroplating it with platinum black. The lightness of the gold leaf receivers made the instrument extremely rugged. Greater sensitivity was obtained for visible radiation by using a receiver of silver leaf tarnished on one side with H2S; however, the sensitivity decreased for wave lengths longer than 1μ.

This publication has 0 references indexed in Scilit: