SU1645906A1 - Capacitive accelerometer - Google Patents

Description

3 .. 1645906

13 and 14. The output voltage of the subtractor 20 is the output voltage of the accelerometer. In the adders 13 and 14, the signal of the amplifier 12 is added to the t analog signal of the source 15 of the reference voltage and is fed to the inputs of the switches 16 and 17 for use in the compensation cycle. The 3 voltage compensation stroke from the adders 13 and 14 through the switches 16 and 17 is fed to the inputs of the hyperbolic circuits of the amplifiers 3 and 9, the output voltages of which are applied to the electrodes 6 and 7 and create a compensating force that returns the sensitive

plate 1 to its original position. 3 il.

The invention relates to an information-measuring technique and can be used to measure accelerations.

The purpose of the invention is to increase speed.

1 shows a functional diagram of the proposed accelerometer; in fig. 2 - its structural diagram in FIG. 3 - timing diagrams of operation.

The capacitive accelerometer contains a sensitive element - a movable plate 1, thin jumpers 2, a base 3, electrodes 4 and 5 on a movable plate, electrodes 6 and 7. on the base, the first and second operational amplifiers (OA) 8 and 9, Phase-sensitive demodulators 10 and 11 differential amplifier 12 with para-phase outputs, the first and second adders 13 and 14, the voltage source 15, the switches 16 and 17, the pulse generator 18, the frequency divider 19, the subtractor 20, the first and second electronic switches 21 and 22, the first and second reference capacitors 23 and 24.

When the accelerometer operates, the following signals are active.

The generator 18 generates pulses with a period T, at the output of the divider Q, pulses with a period of 2T are formed (Fig. 3). At the pulse output of the source 15 of the reference voltage 15, a pulsed two-pole voltage Uou (Fig. 3) is formed with amplitude and period T0.

The accelerometer operates periodically in two cycles: the measurement cycle of Toi (switches 16 and 17 in position a) and the compensation cycle TUK. (switches in position b), and is illustrated by the time diagrams of FIG. 3.

In the measurement cycle (Tots), the switches 16 and 17 and the keys 21 and 22 are in the position a, and the inputs U0 (j. The output voltages of the amplifiers Di), and Di, are rectified (and) phase-sensitive demodulators 10 and II with filters (P.C) at the output and are fed to the inputs of differential amplifier 12. Differential voltage Dih t: M UX2. It is boosted, and the output voltages of the amplifier U x and U k are added to the reference U0 in adders 13 and 14 and subtracted in the subtractor 20. The difference is 0

five

0

life u,

five

0

five

U

Xi

- and

X2

is an output informative voltage. Amount

voltages UQ + Uxi and Uo + UX2. noc blunt to inputs b of switches 16 and 17 and serves to compensate for the measured acceleration.

In the compensation cycle (Current), the switches 16 and 17, the keys 21 and 22 are in position b. The voltages U0 + U and U0 + UXЈ enter the inputs of the hyperbolic circuits of amplifiers 9 and 8, and their output voltages U, and UK2 are applied to electrodes 7 and 6 and create a compensating force Fn, which returns the sensitive plate 1 to its initial position.

The interrelation of the links of the accelerometer balancing system is shown in the block diagram (Fig. 2).

The measured acceleration X vrz- acts on the mass t0 of plate 1 (figure 2) and is converted

by virtue of F „

ha x o

Force F. is balanced by force - RC of electrostatic compensation. The difference in force DG FX – FK through an elastic jumper 2 with stiffness W is converted into an offset X, which causes a change in the capacitances between the electrodes 5 and

WITH

x

Xfc

O s SG + x

6o S

t; gx 51645906

and electrodes 4 and 6 F

 where Јj dielectric

usr el

the force is proportional to the output voltage and does not depend on the gap between the electrodes.

The structural diagram (Fig. 2) contains a direct conversion circuit with

air permeability, S electrode area; $ Q - the gap between the electrodes.

The change in capacitances in the measurement cycle is transformed by a hyperbolic 10 transmission coefficient K to a circuit with amplifiers 3 and 9 in the converter, g f. x and feedback circuit

chesky signals: Dih, Ufl (Ј + x) ... 1 .. n 2UeC0

2

y- x

and AUXe, uo-gl - (. x)

6oS

Where

by fi. Caffey So

15 open-loop transform

0 | and С QЈ capacities of the reference condensates, i.e. the quality factor of it. The transmitters 23 and 24. The voltages of Lx and the voltage are rectified by the phase-sensitive demodulators 10 and 1 and their output voltages are fed to the inputs of the differential amplifier 2.

Differential voltage dich is the force K times and output voltages Un and U

is the value of

g 1

l k U0 Co kr th

W

(Ј0 s

const,

one

4U0- Co

and the measured acceleration x - x

m0-L0

x ux.

X4 and ux Equal in magnitude and opposite in sign, summed up to 25 (j, o rumulac and and in the compensation stroke are fed to the inputs of the hyperbolic circuit - amplifiers 3 and 9, the output voltages of which

the invention

Capacitive accelerometer containing base, cover, sensitive movable plate of monocris

Xi

L o + UX,

) fV (0 + X) nUK2

- (uo + ux) x).

Thus, in the measurement cycle, a hyperbolic linearization circuit is included in the direct conversion circuit of moving X into an electrical signal AU) (in the compensation cycle it is included in the feedback circuit to form compensating voltages U and U "Ј, which create compensating forces:

g

The sensitive element I is affected by the difference in the forces FK F «« - -. Рц4, which at Ux, x2 is Equal

F

2G0Sv .. F Ux i compensating

the force is proportional to the output voltage and does not depend on the gap between the electrodes.

The structural diagram (Fig. 2) contains a direct conversion circuit with

K transfer ratio

2

y- x

... 1 .. n 2UeC0

by fi. Caffey So

open conversion circuit

systems, i.e. good quality of it.

 systems, i.e. soundly

is the value of

g 1

l k U0 Co kr th

W

(Ј0 s

and the measured acceleration

the invention

(j, o rm at l and

Capacitive accelerometer containing a base, a lid, a sensitive movable silicon monocrystal plate connected to the base by jumpers, insulated electrodes in the base, lid and on both sides of the movable plate, as well as the first reference capacitor,

electronic switches, operation; e amplifiers, pulse generator, frequency divider, first adder, reference voltage source, characterized in that

increase the speed, a second reference capacitor, a second adder, pha-sensitive demodulators, a subtractor, switches, a para-pha differential amplifier, and the outputs of the first and second KOMMyTatopoB are connected via the first and second reference capacitors to the inverse inputs respectively, the first and second operational amplifiers, in the negative feedback circuits of which include movable and fixed electrodes of each side of the movable plate and roofs and, the outputs of the first and second operational amplifiers, respectively, through the first and second electronic switches and the first and second phase-sensitive demodulators are connected to the non-inverse and inverse inputs of the differential amplifier, respectively, the first and second outputs of which are connected to the first inputs of the first and second adders, respectively. connected to the second inputs of the first and second switches respectively, {the first inputs of which are connected to the pulse output of the voltage source, analog output d which is connected to the second inputs

U an

.I ,,

и1 /////////, Ш /// ШР ъ.

adders, and the control input - with the control outputs of the phase-sensitive demodulators, the input of the frequency dividers and the output of the pulse generator, the output of the frequency divider is connected to the control inputs of the switches and electronic switches, and the first and second outputs of the differential amplifier are connected to the inputs of the subtractor, the output of which is the output of the accelerometer.

FIG I

Fig 3

Claims (1)

o r m u l a s A capacitive accelerometer containing a base, a fastener, a sensitive movable plate made of monocrystalline silicon, connected to the base by jumpers, insulated electrodes in the base, cover and on both sides of the movable plate, as well as the first reference capacitor, 25 electronic keys, operational amplifiers, a pulse generator, frequency divider, first adder, reference voltage source, characterized in that, in order to improve performance 40, a second reference capacitor, a second adder, of phases sensitive demodulators, a subtractor, switches, a differential amplifier with a paraphase output, while the outputs of the first and second switches are connected respectively through the first and second reference capacitors to the inverse inputs of 50 respectively of the first and second operational amplifiers, in the negative feedback circuit of which I include the movable and fixed electrodes of each side of the movable plate · 55 lengths and covers, the outputs of the first and second operational amplifiers, respectively, through the first and second electrons The keys and the first and second phase-sensitive demodulators are connected respectively to the non-inverse and inverse inputs of the differential amplifier, the first and second outputs of which are connected to the first inputs of the first and second adders, respectively, the outputs of which are connected to the second inputs, respectively ^<1 ' ^t ' ^g ' ^g Venio first and second switches (first inputs of which are connected to the pulse output of the reference voltage source, the analog output of which is coupled to second inputs of adders, a control input - a driving Care and phase-sensitive demodulators, the input of the frequency divider and the output of the pulse generator, the frequency divider output coupled to control inputs of switches and electronic switches, and first and second outputs of the differential amplifier are connected to inputs of a subtractor whose output is the output of the accelerometer.