An IMPROVEMENT i n the WAVE FORM of the AUDIO OSCILLATOR CREIG S. HOYT Grove City College, Grove City, Pennsylvania
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N THE determination of electrolytic conductance, an alternating current is employed in order to prevent the deposition of gas films upon the electrodes and the production of acid and base about them. The alterations in the resistance of the electrolytic
circuit as a consequence of electrode reactions due to real variations in the conductance and to the back potentials set up a t the electrodes are called polarization effects. The polarization is reduced to a minimum by applying a coat of platinum black to the electrodes and
by employing a current of high frequency. It is also desirable that the current source should he such as to give a pure sine wave form free from harmonics and with no unidirectional component. One of the more satisfactory sources of alternating current for conductance measurements is the audio
and any unidirectional component removed by a simple process of mechanical damping of the vibrator, insufficient to destroy the fundamental but adequate to eliminate the harmonics. Figure 2 shows the wave form of the same oscillator as in Figure 1with a Number 5 pure gum rubber stopper resting on the fork and a weight of twenty grams applied to the top of the stopper. I t is essential that the damper be resilient, and the rubber stopper is by far the most satisfactory material employed. The effect of mechanical damping is apparent in the greater precision of location of the balance point on the
oscillator, sometimes called the microphone hummer. The frequency is held constant by using as the vibrator an electrically actuated tuning fork. I t has been recognized that the wave form of this instrument is not pure as shown in Figure 1. This interferes with the determination of the balance point on the Wheatstone bridge. This can be measured by noting the number bridge by the use of a tuned phone as the detector. The impure wave form of the audio oscillator ap- of divisions through which the contact point may be pears to be due to whip in the fork; apibration of a moved without a detectable change in the tone intensity part of the fork with a period diierent from that of the in the phone. This simple device achieves a material fork as a whole. The wave form of the oscillator out- improvement in the precision of the determination of put can he greatly improved, the harmonics eliminated electrolytic conductance.
