Abstract :
The paper forms a natural continuation of an earlier investigation of the electrical stability of condensers and the development of satisfactory means of obtaining compensation for temperature variation. It has been shown in a previous paper that such compensation can readily be obtained for slow temperature-changes, but that great care is necessary in matching the thermal masses of the various parts if the temperature-changes are rapid. By applying the results of this previous analysis, a condenser of reasonable size has been developed which is compensated for temperature-changes as rapid as 7 deg. C. per minute. Special design features are introduced to produce this result, the most noticeable of which are the use of springloaded steel balls in place of plain bearings and the inversion of the normal electrical connections to rotor and stator, this latter alteration being adopted to eliminate difficulties which arise with an earthed screening case. Electrical tests of the performance under varying conditions of temperature-change show that the temperature coefficient of capacitance can be adjusted to have any value between the limits + 80 and ¿ 80 parts in a million per deg. C. and therefore that the coefficient can be so adjusted as to compensate for the inductance coefficient of the associated inductance coil. The variation of the resultant frequency coefficient of the complete circuit with change of oscillation frequency is not large, and the transient variations do not exceed 10 parts in a million per deg. C. for temperaturechanges at a rate of 7 deg. C. per minute.
