An electrical circuit based on analog computer principles has been designed that calculates spectrographic results directly from spectral line transmission values. It operates by solving the equation of the working curve of the element under analysis which must be a straight line in the range that includes all the percentage values of interest. If not straight, the intensity ratio of the analysis and standard lines can be calculated and percentage read from the working curve. Corrections for background and variation in emulsion response with wavelength can also simultaneously be included in the calculation.
S. Epstein, "An Electrical Spectrographic Calculator," Appl. Spectrosc. 14, 7-11 (1960)