Storage circuit for photometer

Claim 1

In an alternating light photometer, especially a single-beam photometer, in conjunction with which a periodically interrupted beam by means of a chopper disk rotated over a motor is incident on a photoelectric transducer, the corresponding output signal of which is amplified and conducted to a display device, in conjunction with which the chopper disk simultaneously releases, alternatively, an illuminating beam for one of two photo-sensitive elements of a switching circuit, by means of which, switches governing two differential current-paths are alternately controllable, wherein the improvement comprises a storage circuit including the output (6) of the photo-electric transducer (3) is connected with both of the inputs (9, 10) of a differential amplifier (OP 3 ) over two parallel, uniform current-paths (7-9; 8-10); that in each of both of the current-paths, in series, a resistance (R 1 , R 2 ) is located, and a condensor (C 1 , C 2 ) in conjunction with one of the switches provided (TR 1 , TR 2 ) as well as between switch and corresponding input of the differential amplifier, when the resistance and the condensor of a circuit-path form a low-pass (R 1 , C 1 ; R 2 , C 2 ) with a time-constant (T) lying appreciably over the connecting or disconnecting time of the beam (1) as determined by the rotational speed of the chopper disk (4); and that the switches over the switching circuit (13) are selectively controlled, that one of them is closed only during the time (T H ) of the complete release, and the other one only during the time (T D ) of the complete interruption of the beam to the photoelectric transducer.