초록 ▼

A capacitance-type electrostatic servo acceleration sensor capable of detecting applied acceleration with high sensitivity and with low error without needing an accurate oscillator. The sensor makes use of a PAM (pulse amplitude-modulation) circuit for performing pulse amplitude-modulation in propor

A capacitance-type electrostatic servo acceleration sensor capable of detecting applied acceleration with high sensitivity and with low error without needing an accurate oscillator. The sensor makes use of a PAM (pulse amplitude-modulation) circuit for performing pulse amplitude-modulation in proportion to the acceleration. The sensor is equipped with a capacitance-detecting portion having a movable electrode and a pair of fixed electrodes located on opposite sides of the movable electrode. The movable electrode is displaced in response to the acceleration. A comparator is formed by an operational amplifier, and a servomechanism is formed. The electrically obtained open gain of this operational amplifier is set sufficiently greater than the mechanically obtained gain of the capacitance-detecting portion. A measurement mode period and a force-balanced mode period are repeated alternately. During the measurement mode period, the movable electrode is not constrained by the servomechanism, and a voltage corresponding to the acceleration is applied to a sample-and-hold amplifier. During the force-balanced mode period, the movable electrode is constrained by the servomechanism according to the output from the sample-and-hold amplifier which corresponds to the acceleration, and the movable electrode is short-circuited to ground.

대표청구항 ▼

A capacitance-type electrostatic servo acceleration sensor comprising: a capacitance-detecting portion having a movable electrode and a pair of fixed electrodes located on opposite sides of said movable electrode, said movable electrode being capable of being displaced in response to an acceleration

A capacitance-type electrostatic servo acceleration sensor comprising: a capacitance-detecting portion having a movable electrode and a pair of fixed electrodes located on opposite sides of said movable electrode, said movable electrode being capable of being displaced in response to an acceleration; a switched capacitor circuit for converting variations in capacitances in said capacitance-detecting portion into an output voltage; a comparator for producing a comparator output voltage so that a difference between said output voltage from said switched capacitor circuit and a given reference voltage becomes 0; a feedback circuit for feeding servo signals back to said fixed electrodes, respectively, of said capacitance-detecting portion, said servo signals being pulse amplitude-modulated according to said comparator output voltage; an output signal-generating circuit for generating an output signal according to said output voltage from said switched capacitor circuit; wherein an operational amplifier forms said comparator and has an inverting input terminal to which said output voltage from said switched capacitor circuit is applied, a non-inverting input terminal to which said reference voltage is applied, and an output terminal, said operational amplifier having an open gain and a voltage feedback ratio; and a feedback circuit connected between said inverting input terminal and said output terminal of said operational amplifier, said feedback circuit providing said voltage feedback ratio so that said electrically obtained open gain is sufficiently greater than a mechanically obtained gain of the capacitance-detecting portion.