A New Approach to Direct Reading Spectrochemical Analysis*

Abstract

A preliminary note on the design and performance of a new type of direct-reading instrument for spectrochemical analysis is presented. A single multiplier phototube is used in combination with a rapid-scanning spectrometer. As the spectral lines cross the single exit slit, voltage pulses are generated by the phototube and are panoramically presented on an oscilloscope whose time-base is synchronized with the spectrum scan. The pulse heights are measured by converting them to “bursts” of constant amplitude pulses whose number is proportional to the magnitude of the original spectral line pulse. This is accomplished by means of a cathode-ray tube, a “comb-grid,” and a secondary multiplier phototube. The pulse bursts corresponding to the lines whose intensity is of interest are separated by means of electronic gates. High-speed scalers and mechanical registers indicate the time integrals of the spectral line intensities. Intensity ratios are automatically computed after the exposure and recorded on a variable span strip chart recorder, which may be empirically calibrated to read directly in percent. Preliminary data indicate that a precision of analysis of ±1 percent can be achieved.