GB912882A - Improvements in or relating to devices for the chemical analysis of materials by means of photocells and by the spectral method - Google Patents

Abstract

912,882. Photo-electric spectrometers. REGIE NATIONALE DES USINES RENAULT. Dec. 19, 1958 [Dec. 21, 1957; Dec. 16, 1958], No. 41089/58. Class 40 (3). In order to investigate the chemical composition of a substance an are or spark discharge between two electrodes, one at least of which is made from the substance, is formed and the spectrum of the light emitted analysed photoelectrically. Apparatus to do this is provided with a first plurality of detectors arranged to receive suitable characteristic lines in the dispersed spectrum from the discharge and a second plurality of detectors receiving spectral rays emitted from reference internal standards. Individual integrating means are operatively connected with each detector and timing means are provided to initiate the charging of integrators associated with certain sample detectors when the integrated value of the output of particular standard detectors reaches predetermined values and to terminate the charging period when other predetermined values are reached. The charges stored in the integrators are then directed to recording means and the values derived give information as to the chemical composition of the sample. Fig. 13 shows a block schematic diagram of one form of apparatus have a press-button programme setting device 120 setting up the sequence of events to be performed by applying pulses to relays in control unit 121 and preparing the required integrator circuits. Photo-multipliers 143, 144, 145 and 146 viewing spectral lines in the discharge are associated respectively with integrators 136, 137, 138 and 139 whilst photomultipliers 140, 141 and 142 viewing reference standards are associated respectively with integrators 122, 123 and 124. The reference standard integrators each feed a detector circuit (125, 126, 127) giving an output whenever the input potential from its integrator is equal to a predetermined reference potential derived from a tapping on potential divider 128. Connected to each detector circuit is a string of time determining devices (129 to 134) which feed reference potentials to the detector circuit in a predetermined sequence and route the output signals produced by that circuit in response thereto to control the integrators associated with the sample. The control unit and various interconnections between units enable switching operations to be performed by relays so that once a programme has been initiated by the pressing of a button on unit 120 the rest of the sequence follows automatically. At the end of the programme the potentials stored on each of the sample integrators used are fed in sequence through the control unit to a recording voltmeter 40. In use the apparatus may be employed in a preliminary examination to measure either the instantaneous intensity of a spectral line or the integral of the intensity over a given period of time. The radiation input investigated may either be from an internal standard or from a sample discharge. Alternatively the energy received by two detectors representing different spectral lines from the sample or one line from the sample and one from an internal standard can be compared. Such preliminary investigations enable the right photo-cells and suitable integration time intervals to be chosen for the analysis of a sample.