Electrometer for measurement of charge, voltage or current - detects mechanical vibrations of non-fixed electrode at fundamental and first harmonic frequencies

摘要

Electrometer for measuring electrical charge, electrical voltage or current has two electrodes one of which is fixed and the other of which is able to vibrate mechanically. A reference voltage is applied to one electrode, pref. by earthing it, and an alternating voltage Vo of frequency fo is applied across the electrode plates. The amplitude of mechanical vibration is detected at the frequency fo. This amplitude is a function of the quantity to be measured. The amplitude of vibrations at frequency 2fo is measured also (34) and a direct voltage V3 is generated (35) whose amplitude is a function of the vibrational amplitude. The voltage V3 is applied to the exciter so as to modify the amplitude of the voltage Vo. The amplitude of the vibration at fo becomes independent of the distance d between the vibrating electrode (3) and the support (1).