A mechanical harmonic analyzer is described which will analyze oscillograms obtained from the cathode ray oscillograph when the reference field is sinusoidal. The instrument is adjustable to take care of oscillograms of various sizes. The analyzer can be used also for curves plotted on a uniform base. The particular instrument described was made to analyze up to and including the tenth harmonic.
C. F. WIEBUSCH, "A MECHANICAL HARMONIC ANALYZER FOR CATHODE RAY OSCILLOGRAMS," J. Opt. Soc. Am. 15, 355-357 (1927)