SU1530999A1 - Capacitance accelerometer - Google Patents

Abstract

The invention relates to instrument engineering and is intended to measure linear accelerations. The aim of the invention is to improve the operation accuracy by eliminating the influence of parasitic electrostatic forces. The goal is achieved in that a capacitive accelerometer, comprising a case, a sensitive element in the form of a plate 1 made together with an elastic suspension — rods 2 and jumpers 3 and 4 — from a silicon single crystal, and a capacitive sensor position consisting of a sensitive element arranged on the housing and isolated electrodes 6 and 7, the block voltage excitation and hyperbolic linearization circuit - an amplifier 10 and capacitance C _0, enter the second pair of insulated electrodes 6 and 9, a second circuit hyperbolic linearization (amplifier 11 and the capacitance C ₀₎ and the subtractor 12 is connected to the outputs of the hyperbolic linearization schemes. In this accelerometer, the parasitic electrostatic forces of the interaction of the electrodes of the capacitive sensor of the position of the sensitive element of the device are mutually compensated in any position of the sensitive element relative to the accelerometer case. 2 Il.

Description

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All sensitive element in the form of a plate 1, made together with an elastic suspension — rod and 2 and jumpers 3 and 4 — from a silicon single crystal, and a capacitive sensor for positioning the sensitive element, consisting of insulated electrodes 6 and 7 arranged on the sensitive element and body , an excitation voltage unit and a hyperbolic linearization circuit - amplifier 10 and capacitance C, a second pair of isolated electrodes are introduced

The invention relates to instrument engineering and is intended to measure linear accelerations.

The purpose of the invention is to improve the accuracy of the accelerometer.

Fig. 1 shows the accelerometer electroconstructive circuit, section AA; in fig. 2 - accelerometer circuit, option.

The accelerometer sensing element is a movable plate 1 with four rod consoles 2 with jumpers 3 and 4 fixed at the ends at the base 5. On both sides of the plate 1 there are electrodes 6. At the base 5 there is a stationary electrode 7, and in the cover 8 - electrode 9. Electrodes, plugs 6 are connected to the inputs of operational amplifiers 10 and 11, electrode 7 is connected to the output of the operational amplifier JO, electrode 9 is connected to the output of amplifier 1 1. The outputs of the operational amplifiers are connected to the input of the subtractor 12. The source 13 of the reference voltage U is through a switch 14 switched by the modulator 15, and the exemplary capacitors C is connected to the inputs of the operational amplifiers 10 and 11.

In the scheme of an acceleleometer (Fig. 2), the electrodes 6 are connected together and connected to the input of the operational amplifier 10, and the electrodes 7 and 9 to the input of the switch 16, controlled through a frequency divider I7 with a division factor n from the modulator 15. The last control switch 14 in the circuit of a source of a constant reference voltage and with a period of modulation T. The outputs of the hyperbolic circuit and the source 18 of the reference voltage are connected

6 and 9, the second hyperbolic linearization scheme (amplifier 11 and capacitance C) and the subtraction unit 12, connected to the outputs of the hyperbolic linearization schemes. In this accelerometer, the parasitic electrostatic forces of the interaction of the electrodes of the capacitive sensor position of the sensitive element of the device mutually compensate for any position of the sensitive element relative to the accelerometer case. 2 Il.

to the input of the differential device 12.

The accelerometer works as follows.

In the absence of a measurable acceleration, X O plate 1 is in the middle between electrodes 7 and 9, i.e. gaps in the tank between the electrodes 6,7 and 6, 9 are equal to So, 8d 8 and Cx - CK. Then, the output voltages of the operational amplifiers are equal to UM and ,,, Uo, and the output voltage of the differential circuit is 12 0. At the same time, the electrostatic interaction forces of the electrodes are equal and mutually compensate.

In the presence of measurable acceleration, X plate 1 is shifted by

& x

X sh

V

where m and W are the mass of the plate and the rigidity of the suspension.

In this case, the capacities take on the corresponding values

EoS

 S o

60 s

 Se + ux

6o is the dielectric constant of the gas filling the housing. accelerometer I S - the area of the electrodes.

Output voltage of op amps

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and,. and,

   Bo Z

(Sn + Lx)

ia uo g% - (So-ux),

and the output voltage of the accelerometer

Thus, when the electrode pairs are identical, the parasitic electrostatic forces, regardless of the movement of the plate 1, are equal and mutually compensate for the entire range of acceleration measurements.

In the scheme of the accelerometer (figure 2; in

position

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output voltage U 0.

When there is a measured acceleration X 0, the plate 1 is shifted by x, the capacitances change, and the output voltage in one modulation half-period is

 - (“+ them)

(5 „- them).

y .. - variable composition of sho

output differential eg - 2Ue Cc

l.i,

o S

-X, i.e. proportional to the measured acceleration. The values of the forces in the voltage pulse are equal

 ,

Selerometers completely eliminated the effect of parasitic electrostatic forces 20, which increases the accuracy of measurement of accelerations and allows significantly expanding the range of measured accelerations down.

Claims (1)

25 claims Capacitive accelerometer, comprising a housing, a sensitive element in the form of a plate, arranged together therein on an elastic suspension 30 with a silicon monocrystal elastic suspension, and a capacitive sensor position sensor, consisting of sensing elements and an insulated electrode housing, an excitation voltage block and a hyperbolic linearization circuit, which includes electrodes to improve accuracy. Pu .Q To avoid the influence of parasitic electrostatic amplifiers, a second pair of insulated electrodes are placed on the accelerometer, located on the other side of the plate, the second circuit g5 hyperbolic linearization, in which this pair of electrodes is included, and a subtraction unit connected to the outputs of hyperbolic linearization circuits. 35 L 9 "/ -5 Fi9.2