SU1561047A1 - Capacitive accelerometer - Google Patents

Abstract

The invention relates to information-measuring technology and can be used in devices for measuring the parameters of movement of objects. The aim of the invention is to increase the measurement limits by one, two orders of magnitude and increase the noise immunity and reliability for this purpose. In it, the sensitive elements — plates are fixed on one axis with the possibility of moving the first sensitive element relative to the second, and the jumpers have an increased rigidity. The accelerometer also has two plates 8 and 9 with electrodes 10 and 11 of a capacitive displacement transducer and electrodes 12 and 13 of an electrostatic compensator. Thus, in the invented accelerometer, the offset of the two moving sensing elements is mutually compensated when the compensator is made only from moving parts. 2 hp f-ly, 3 ill.

Description

(21) 4250213 / 24-10

(22) 04/13/87

(46) 04.30.90. Bksh. Number 16

(71) Leningrad Polytechnic Institute. K.I. Kalinina

(72) V.M.Artemov, V. „E.Evdokimov, V.I. Loban and V.S. Moiseichenko (53) 531.768 (088.8)

(56) USSR Author's Certificate No. 1138746, cl. G 01 R 15/08, 1983.

Patent of Great Britain No. 2047902, cl. G 01 P 15/13, 1980.

USSR author's certificate “1067445, cl. G 01 R 15/13, 1984.

(54) CAPACITIVE ACCELEROMETER

(57) The invention relates to information-measuring equipment and can be used in devices measuring

7 6

th

.

,

sweat

four.

parameters of motion of objects. The aim of the invention is to increase the measurement limits by one, two orders of magnitude and increase noise immunity and reliability. Sensing elements - plates are fixed on one axis with the possibility of moving the first sensitive element relative to the second, and jumpers have increased rigidity. The accelerometer also has two plates 8 and 9 with electrodes 10 and 11 of a capacitive displacement sensor and electrodes 12 and 13 of an electrostatic compensator. Thus, in the accelerometer, the displacement of two moving sensing elements is mutually compensated when the compensator is made only from moving parts. 2 hp f-ly, 3 ill. I

72

/ J

15 G5

/

with

0

(L

SP

about

4b

11 M1b

FIG. one

15

20

25

The invention relates to information measuring technology and can be used for accurate measurements of linear accelerations, accelerations, gravity, and motion parameters of objects.

The aim of the invention is to expand the range of measured accelerations due to partial compensation of the measured JQ acceleration with a small difference in the masses of the sensitive elements, increased noise immunity and accelerometer density, and expansion of the upper limit of the measured accelerations.

FIG. H, 2 shows the constructive scheme of the proposed axometer; in fig. 3 - structural.

| Accelerometer contains the first sensitive element - plate 1, fixed with two bars, 2, the second sensitive element 3i fixed by jumpers 4 with a non-moving base 5 of silicon monoplates installed in the case 6 and clamped by a cover 7. According to the first variant on the sensitive element 3i Additional plates 8 and 9 are fixed on both sides with electrodes 10. And And and electrodes 12 and 13. On plate 1 are located on both sides electrodes 14 and 15 opposite to the corresponding electrodes placed on plates 8 and 9. Electrodes Holes 10, 11, and 14 form a capacitive sensor for the relative movement of sensing elements 1 and 3 and include a differential circuit of the measuring bridge 16. The bridge output is connected to the input of the differential amplifier 17c with a phase-sensitive rectifier whose output voltages are 4U and -Ux. with a constant voltage U0 of the source 18 of the reference voltage, and are supplied to the electrodes 12, 13 and 15 of the electrostatic compressor.

The accelerometer works as follows.

In the presence of measurable acceleration K, the sensitive elements 1 and 3 C, with masses m and w, are influenced by forces and F, which cause displacements X 1 and X5 of plates 1 and 3, respectively, by angular rotation at angles tp (and tf, (t .e. Hch 1, Cf, and He I, tp3). Moving, X and He calculated

35

40

50

55

0

five

are scattered by a capacitive sensor for the relative movement of sensitive elements. The difference in displacements X, | 5X4 - X5 is converted by the measuring circuit of bridge 16 into an electrical signal uUx, which is amplified and rectified by amplifier 17, the output voltages + UX and UX of which are applied to the electrodes 12, 13 and 15 electrostatic compensator. The electrostatic attractive forces between the electrodes 12 and 15, 13 and 15 are respectively

CH gggi ° and V c; io them

where Ј is dielectric constant

environments between the compensator electrodes;

S is the area of the smaller compensator electrode;

and about

0. - the distance between the electrodes,

The forces FKi and FK, acting on the sensitive elements 1 and 3, cause, respectively, displacements

X

 ESJL „v K1 W and AKa W2

five

where W, W - stiffness of the jumpers 2 and

4 respectively. Compensating displacement x k

 HK - xy

1 Equation -CoHk compensation or

 C - i - - ZiL

X (

w, w

W.

w

40

At W, W2, the measured acceleration is determined by the expression

X

ЈSU0UX

.l ()

0

five

According to the second variant, plate 8 with electrodes can be fixed on one sensitive element, and plate 9 with electrodes on another. Then the masses of the sensitive elements can be made slightly different from each other, which allows for small values of the compensating force to measure arbitrarily large values of the measured accelerations,

Thus, in comparison with the known accelerometers with electrostatic compensation, the measured acceleration value offered by the same value of the compensating force is 2 / (1 - -) times larger. With mi

the same elastic suspensions, the same manufacturing technology, high stability of the elastic characteristics of a silicon single crystal, the uniformity of the rigidity of the suspensions is maintained with high accuracy and the error of the proposed accelerometer is determined mainly by the errors of the electrostatic compensator, as in the known compensation accelerometers. In addition, the magnitude of the mutual displacement X between the moving electrodes of the electrostatic compensator is an order of magnitude smaller than the displacements X and Xs of the sensitive elements, which makes it possible to reduce the gap between the electrodes of the compensator and thereby increase the compensation force.

Claims (3)

1. Capacitive accelerometer containing a fixed base made of one single crystal of silicon, two sensitive elements in the form of plates connected to the base with the help of equi-peak devices 0 five 0 five 0 five small cases, as well as a housing, a cover, a capacitive displacement transducer, a compensator and an output signal processing circuit with an amplifier and measuring bridge, characterized in that, in order to increase the range of measured accelerations, increase noise immunity and reliability, two additional plasmas are introduced - tines with electrodes of a displacement sensor and an electrostatic compensator fixed on them on one side, the opposite electrodes of which are fixed on one or two plates of sensitive elements located between d Additional plates. 2. The accelerometer according to claim 1, characterized in that both additional plates are fixed on one sensitive element, and the electrodes of the displacement sensor and compensator are on both sides of the other sensitive element. 3. Accelerometer according to claim 2, in order to expand the upper limit of the measured accelerations, one additional plate is rigidly connected to the first sensitive element and the other to the second, with the electrodes of the compensator and the displacement sensor fixed to both sensitive elements on one side . FIG. 2  X Fig.Z Editor M. Bandura Compiled by A. Polynkov Tehred M. Didyk Proofreader S. Shevkun Order 976 Size 454 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 U0 13 Subscription