On the Measurement of Natural-Frequency of an Inductance Coil at Audio-Frequency

Abstract

By Campbell's frequency bridge, we measure the frequency of the alternating current by known mutual inductance. and capacity. The same circuit can be utilized to determine the natural frequency of a coil used as the primary of the mutual inductance, knowing the frequency of the current and the capacity, which gives the balance. In the experiment described in this paper, the frequency is determined by standard tuning forks.
A theory by which the natural frequency and the self-capacity of the primary coil can be obtained by taking the balance at two known frequencies is worked out the actual method of experiment and the experimental check of the theory are described.
When the sharpness of the balance is greatly affected by the effect of the selfcapacity, it can be improved by a simple modification of the circuit as shown in Fig. 6. (Jan, 1924, Sendai, Japan)