Principles of a New Portable Electrometer

The fundamental principles underlying the operation of a new type of portable electrometer are given. It is shown that the periodic transfer of static charges from one capacity system to another and back again can be used to produce an alternating electrical potential. The alternating potential is amplified by means of vacuum tubes, then rectified by a synchronous commutator and the resulting direct current used to operate an indicator. Instruments with capacities of about 25 cm and sensitivities of ${10}^4$ microamperes per volt have been built to operate with portable microammeters used as the indicator. The period of the device depends on the indicator employed and is small.