An Oscillograph for Ten Thousand Cycles

the past, oscillographs have been over a INrange extending and effortslittleobtain aemployedrange havefrequency only to a below the natural frequency of the vibrating element, to wider been di- rected toward raising the resonant frequency of the vibrator. In the present paper there is described a new method of attack that obviates many of the difficulties and restrictions previously encountered. In brief it consists in equalizing the natural characteristics of the string by electrical networks inserted in the circuit. One part of the network equalizes for the fundamental resonance Fo, and another equalizes the range above this frequency. Other factors enter to limit the upper frequency obtainable, but practically flat characteristics are secured up to about two and one-half times the fundamental frequency of the vibrator. The new oscillograph arose from efforts to extend the frequency range of the rapid record oscillograph (Fig. 1) already described. This instrument was of the string type, and before electrical compensation could be applied, a complete study of the string characteristics of the galvanometer was necessary. If a measurement is made of the deflection of the string by an alternating current of constant value but variable frequency, it is found that the sensitivity increases enormously in the region of its fundamental resonance frequency (F ) and that there are subsidiary resonance peaks occurring at approximately 3F , 5F , 7F , and so on. No signs of resonance appear at even multiples of the fundamental fre1 0 0 0 0 Electronics, August 1931, p.