A means of controlling spark excitations has been devised for the purpose of improving the accuracy of spectrochemical analysis. The system applies to currently popular air-interrupted sources regardless of the type of analysis being performed. The control procedure consists of resolving and counting individual spark discharges to determine an exact discharge rate. Previous control methods have depended on an ammeter and oscilloscope which neither indicate discharge rate accurately, nor resolve random irregularities in rate. Reproducibility of the discharge rate can provide an improved means of repeating spectral line intensities as required for quantitative analysis. The control system consists of a phototube pickup triggering an electronic scaling circuit. Illumination from the spark discharge produces the phototube signal. Individual discharges are counted to provide an indication of the exact spark discharge rate per unit time.
F. R. Bryan and E. F. Runge, "A Method of Monitoring Spectroscopic Sources," Appl. Spectrosc. 11, 64-67 (1957)