FORCE BALANCE INSTRUMENT WITH ELECTROSTATIC CHARGE CONTROL

摘要

A force balanced instrument, such as an accelerometer, employs a pendulous mass having combined electrostatic pickoff and forcing plates on opposite sides thereof. The plates provide a constant attractive force in successive periods acting alternatively on opposing sides of the sensitive element. Force balance is achieved by controlling the duty cycle so that the difference in duration between each of the parts of a full cycle is a linear measure of acceleration. Voltage on each of the forcing plates is sensed independently immediately after each is charged with a fixed charging pulse which provides a fixed force level over the duration of the part cycle. The two successive voltage samples are stored, and the difference between them integrated to control the duty cycle of a pulse width modulator, which itself controls the duration of application of the alternately directed forces applied by the respective plates to the pendulous mass.