D. C. electrometer

摘要

Feedback circuit for the probe of an d.c. type electrostatic voltmeter to reduce spacing sensitivity thereof. A variable gain amplifier is employed to control the amplitude of the a.c. signal output of a square wave oscillator in response to the potential sensed by the probe. The a.c. signal output drives a high voltage transformer, the output of which is rectified to provide a d.c. signal output matching the potential sensed by the probe. The d.c. output is returned to the probe housing to bias the housing to a potential equal to the potential read by the probe. A sample and hold circuit enables readout of the d.c. signal output.