GB346620A - - Google Patents

Abstract

346,620. Pyrometers. SOC. C.E.M.A., 236, Avenue d'Argenteuil, Asnieres, Seine, France. June 25, 1930, No. 19361. Convention date, July 16, 1929. [Class 97 (iii).] To measure temperature, the effect of radiation from a distant hot body on a photo - electric cell is compared with the effect of radiation from a standard source. The variations in resistance of the cell due to radiation from the hot body are amplified and read by a milliamperemeter. An equal deflection of the milliamperemeter is then obtained by exposing the cell to the standard source and varying the voltage applied to the source. The voltage thus applied is a measure of the temperature of the hot body. Alternatively the distance of the standard source from the cell may be varied or the source may be fixed and fitted with an adjustable diaphragm. Thermometric calibration is effected by sighting the opening of a furnace containing fusible cones. The Figure shows one form of apparatus for carrying the method into effect. The metallic casing 1 is carried by and turns in the bracket 4 which can be orientated on the stand 2. Sights 24, 25 direct the casing towards the hot body, the radiation from which passes through the lens 10 to the cell 11. A mirror 12, the position of which is indicated by pilot lamps 22, 23, is adapted to turn so as to cut off the radiation from the hot body and reflect the radiation from the standard source 13 on to the cell. The voltage applied to the lamp 13 is adjusted by the potentiometers 15, 16 and indicated by the voltmeter 14. The cell 11 is included in a Wheatstone bridge and its variations are amplified by the three-electrode valve 17 and indicated by the milliamperemeter 6. A potentiometer 28 for bringing the valve 17 to its most sensitive state is included in the Wheatstone bridge. A diaphragm adapted to be adjusted according to the emissive power of the hot body is placed in front of the lens 10. A filter, allowing only infra-red radiations to pass and having a diaphragm cutting out the edge of the sensitive portion of the cell is preferably used. A piece of opal glass may be placed in the plane of this diaphragm.