The instrument is light and portable, and can be sighted as easily as an opera glass. The telescope, which is held in the hand, weighs only 25 oz.; and the case containing the battery, rheostat and milliammeter, which is slung from the shoulder, only 10 lb.
FIG. 119.—Thermocouple in floor of furnace.
FIG. 120.—Pyrometer in gas furnace.
A large surface to sight at is not required. So long as the image formed by the objective is broader than the lamp filament, the temperature can be measured accurately.
FIG. 121.—Tycos multiple indicating pyrometer and recorder.
