SU1249319A1 - Capacitive transducer of angular shifts with variable gap - Google Patents

Abstract

The invention relates to a measurement technique and makes it possible to determine with improved accuracy the stability of given angles in time or their variation under the influence of external factors when using a capacitive converter of angular mixing, variable gap. This transducer contains a moving electrode in the form of a wedge with two conducting edges, mounted between two stationary electrodes with the possibility of a turn around their common axis. Both conductive faces of the wedge-shaped moving electrode are electrically connected and connected to the input of the equilibrium detector of a bridge capacitance measuring circuit of the converter. The detector output is connected to a movable contact of an adjustable secondary winding of a supply transformer wound to the winding of this transformer, having a constant number of turns and connected to fixed electrodes of a capacitive angle sensor. When the angular position of the moving electrode changes, the balance of the measuring bridge circuit is disturbed, which is restored by the signal from the equilibrium detector by changing the number of turns of the secondary winding of the supply transformer. The accuracy and temporal stability of a capacitive transducer with a variable gap is due to the fact that its output signal depends only on three sufficiently stable and highly accurate values: the number of turns of the secondary windings of the supply transformer and the set angle of installation of two hydroelectric electrodes of the angle sensor. 1 il. b (L to 4 with SA;

Description

The invention relates to a measurement technique and can be used in various fields of engineering and industrial production for measuring angular displacements, determining the stability of given angles in time, or variations thereof under the influence of external factors.

The purpose of the invention is to improve the accuracy of conversion by eliminating the influence of the dielectric constant of the medium in the interelectrode space of the capacitive converter and eliminating the influence of the instability of the capacitance of an exemplary capacitor included in the bridge circuit for measuring and converting the signal of the capacitive converter.

The drawing shows a schematic diagram of a capacitive angular displacement transducer with a variable gap.

The converter contains a capacitive angle sensor with two flat stationary electrodes 1 and 2 mounted on 20 insulating plates 3 and 4 at an angle to one another and having a common axis of rotation 5, the central line 6 of which is aligned with the line of intersection of the planes that are the continuation of active internal

The winding of the winding 20, bl, is provided for their opposite connection. Two other measurement circuits are formed and Cr between the active conductors of the electrodes 1.11 and 2.11, the values of which are defined by oCi. and oCj, between these elec

The converter works in the same way.

Let the measurement circuit be in the initial position. When rotating, the wedge-shaped electrode 11 connected to a trol (not shown), for example, the arrow, the angle oCi increase oCj, decreases. Accordingly, Xci resistance increases, decreases. Upon a signal, the child is provided with a cloak; the adjustable winding 21 is set to balance its measurements. The number of inclusions of the winding 21 determines the placement of the electrode 11, corresponding to oti.

According to the Gauss theorem

C.l

oLl

The surfaces 7 and 8 of the electrodes 1 of the resistance X ct and X are equal and 2, and are located at the same distance from them. The electrodes 1 and 2 are shielded from the outside by, for example, metallizing the surface of the carrier plates 3 and 4 and forming screens 9 and 10 on them.

ShGV-6G both

thirty

X

gujte- n

where w is the circular frequency of the voltage

power measurement circuit; - dielectric constant

interelectrode environment; B - the width of the active surface

sensor electrodes;

rH and rH is the distance to the outer and inner edges of the active surfaces of the electrode 1 of the sensor. The equilibrium condition of the bridge circuit with between fixed electrodes 1 and 2 is installed with the possibility of angular movement relative to the common axis of rotation 5, the third electrode 11, made in the form of a wedge with two conductive active surfaces 12 and 13, the line of intersection of the continuation of the planes of which is aligned with the central line 6 of this axis. The active surfaces 12 and 13 of the wedge-shaped movable electrode 11 are surrounded by guard electrodes 14-17 connected to ground 40, determined by the tire ratio, and electrically interconnected by a jumper 18 connected to the input of the detector 19 of the equilibrium bridge sensor measuring the capacitance of the angle sensor.

The two arms of this circuit are formed by two secondary windings 20 and 21 of the supply transformer 22, the first of which is made with the same and second (with an adjustable number of turns. The outputs of the first winding 20 of the transformer are connected to fixed electrodes 1 and 2 of the capacitive angle sensor one of these leads is also connected to the regulated tap of the second secondary winding 21 of the supply transformer, to which

(3)

45

Hs, Pa g pgo - p g

gdepgd-the number of included turns of the adjustable secondary winding 21, supplying the transformer 23; - the total number of turns of the winding 20 of this transformer. According to equalities (1) - (3), the measured angle of rotation ОС is determined by the relation

, ctj-f-oti

 Nth

 tl20

(four)

Since for this construction oij.-f о (.г const, the angle ot-i, as it follows from the detector 19 of equilibrium 55 (4), is also unambiguous, and the linear circuit that controls the switching function included turns 21 adjustable secondary winding of the supply transformer.

turns of the adjustable winding 21. The direction of the winding of the winding 21 opposite direction

winding of the winding 20, due to which they are provided with a counter-consistent connection. The two other arms of the measurement bridge circuit are formed by capacitors Ci and Cg between the active conductive surfaces of the electrodes 1.11 and 2.11, respectively, whose values are determined by the angles oCi. and oCj, between these electrodes.

The Converter operates as follows.

Suppose that in the initial position the bridge circuit is in equilibrium. When the wedge-shaped moving electrode 11 connected to the control object (not shown) is rotated, for example, counterclockwise, the angle oCi increases, and the angle oCj decreases. Accordingly, the capacitance Xci increases, the capacitance Xcj decreases. The signal from the equilibrium detector 19 provides for the switching of the turns of the adjustable winding 21, so that the equilibrium of the bridge measurement circuit is restored. The number of turns of the winding 21 turned on determines the angular displacement of the electrode 11, corresponding to the angle oti.

According to the Gauss theorem, the capacitances X ct and X are equal

C.l

oLl

opposition X ct and X are equal

ShGV-6G both

(12)

X

gujte- n

where w is the circular frequency of the voltage

power measurement circuit; - dielectric constant

interelectrode environment; B - the width of the active surface

sensor electrodes;

rH and rH is the distance to the outer and inner edges of the active surfaces of the electrode 1 of the sensor. The equilibrium condition of the bridge metering circuit is determined by the ratio

the measurement is determined by the ratio

(3)

Hs, Pa g pgo - p g

gdepgd-the number of included turns of the adjustable secondary winding 21, supplying the transformer 23; - the total number of turns of the winding 20 of this transformer. According to equalities (1) - (3), the measured angle of rotation ОС is determined by the relation

, ctj-f-oti

 Nth

 tl20

(four)

The advantage of the capacitive angular displacement transducer of the proposed design is the increased measurement accuracy and independence of the readings from destabilizing factors, because according to the reduced conversion function (4), the measured angle depends on only three sufficiently stable values: the number of turns of the two fixed electrodes which can be determined with high accuracy. By providing close inductive coupling between the two secondary windings of the supply transformer entering the bridge measuring circuit, the ratio of their turns and the voltages taken from them is performed with an accuracy of 0.001-0.002%. In view of this, the accuracy and temporal stability of the proposed capacitive transducer is increased in comparison with the known ones by a factor of 3-5.

Claims (1)

Invention Formula A capacitive angular displacement transducer with a variable gap, which contains a capacitive angle sensor with two shielded flat electrodes on the outside, installed at an angle to one another and having a common axis of rotation. the central line of which is aligned with the line of intersection of the planes, which are a continuation of the active internal surfaces of the electrodes, and is located at the same distance from them, and the bridge circuit for measuring the capacitance resistance of the sensor, which includes a supply transformer with two secondary windings, is first of which are made with the same, and the second - with an adjustable number 0 turns, and an equilibrium detector of a bridge circuit connected to the output of the second winding, characterized in that, in order to increase the conversion accuracy, it is equipped with a third electrode installed with the possibility of angular movement relative to a common axis of rotation and made in the form of a wedge-two conductive active surfaces whose continuation lines of planes are aligned with the center line of this axis, the first 0 two electrodes are fixed and connected to the terminals of the first secondary winding, one of which is also connected to an adjustable tap of the second secondary winding, made with the opposite winding direction, and both conducting 5, the active surfaces of the third electrode are electrically connected and connected to the input of the equilibrium detector. 22 Editor M. Blanar Order 4223/40 Compiled by S. Skrypnyk Tehred I. VeresKorrektor G. Reshetnik Circulation 670 VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab. 4/5 Branch PPP Patent, Uzhgorod, st. Project, 4