A Compensated Thermionic Electrometer

A compensated single tube electrometer is described and the principles of its operation discussed. This apparatus has been found to compare favorably with “balanced tube” circuits both as regards stability and sensitivity and to be superior in many respects to the quadrant electrometers which usually have been used for the measurement of small currents, high resistance, or of voltage in circuits of high resistance and in those cases where only an infinitesimal current may be drawn from the source of the electromotive force. For most measurements the degree of compensation afforded has been found to be sufficient to make possible the use of dry cells or even properly controlled rectified alternating current as a power source.