| 摘要 |
<p>1,188,630. Photo-electric absorptiometers. COMMISSARIAT A L'ENERGIE ATOMIQUE. July 25, 1968 [Aug.4, 1967], No.35602/68. Heading G1A. In a null balance two path absorptiometer an optical wedge in the reference path is shifted by a pulse motor energized by an oscillator with a frequency proportional to the amplitude of the out of balance signal. Light from a monochromator 3 is switched alternately through a sample 6 and an optical wedge 7 to fall on a photocell 8 connected to a phase sensitive rectifier 9. The oscillator 11 has two channels each comprising transistor-capacitor relaxation oscillators having a frequency controlled by the magnitude of the output of rectifier 9 (one channel if the output is positive, the other if negative). The pulses are fed to a step-by-step wedge motor 13 and an up/down counter 14. The count may be used retro-actively in a chemical process control or to give an alarm at a pre-set value. Automatic titration The absorptiometer may be associated with an automatic titrimeter in which an oscillator energizes a step-by-step motor of a mechanical burette so as to record volume against absorption on a two channel recorder. Alternatively the burette motor may be stopped when a pre-set count on counter 14 shows that the end point has been reached. If the end point corresponds to a point of inflexion on the absorption curve, it may be detected by applying the pulses to a ratemeter and differentiator.</p> |
