GB826981A - Improvements in or relating to photometers - Google Patents

Abstract

826,981. Photo-electric photometers. LEITZ G.m.b.H., E. Aug. 31, 1956 [Sept. 2, 1955], No. 26637/56. Class 40 (3). A photometer comprises two bolometers 64 connected in push-pull, which are alternately irradiated, first by light (from a source 53) which has passed through a sample cell 60 and then by light from the same source which has passed through an empty comparison cell 59. The light is split by a partial mirror 54 and alternately reflected and passed by a rotating mirror 57 to a monochromator 58 whence it is reflected alternately at a higher speed to each bolometer 64. An alternating current is set up in a transformer 65 which is amplified at 66. Eccentrics keyed to the rotating mechanism 62 operate switches 23 and 68 which control a circuit 69 comprising two capacitors shunted respectively by a potentiometer 24 and a resistor, the charging of one capacitor being delayed (by a line of inductances and capacitors) so that both are charged and discharged synchronously, an adjustable resistor for compensating voltage losses and a further potentiometer varying the time constant. The output 51 of the circuit representing the quantity to be determined is amplified at 71 to energize a servomotor 70 to zero the tapping of the potentiometer 24. The quantity is also recorded. Ring modulators controlled by waste light from the mirrors 57, 61 may replace the switches 23 and 68. Photo-cells or thermocouples may replace the bolometers. A mirror arrangement is described wherein one mirror is mounted on a hollow shaft through which extends a further shaft on which is mounted the other mirror which rotates by friction with the edge of the first mirror (Fig. 3, not shown).