SU1325299A1 - Photoelectric displacement transducer - Google Patents

Abstract

The invention relates to the field of measurement technology and can be used to measure movements using photopotentiometers. The purpose of the invention is to increase the measurement accuracy by eliminating random faults caused by the non-uniform conductivity of the photoconducting layer. The switching unit 8 has the ability to connect to the second output 21 of the first photopotentiometer 11 both the first output 22 of the second photopotentiometer 12 and its second output 23. The differential photoreceiver 3 is simultaneously included in the first and second measurement bridges 4 and 6. Such inclusion of photopotentiometers 11, 12 into the bridge circuit 4 of measurement makes it possible to compare their characteristics and take into account the relative non-uniformity of conductivity of the photoconductive layer of photopotentiometers at the time of transformation of the position of shadow mask 2. 3 Il. (L So ate GchE So So

Description

The invention relates to the field of measuring technology and can be used to measure displacements using photopotentiometers.

The purpose of the invention is to increase the measurement accuracy by eliminating random faults, due to the non-uniform conductivity of the photoconductive layer of the photopotentiometer.

FIG. 1 shows a photoelectric displacement converter circuit; in fig. 2 is a schematic diagram of a photoelectric displacement transducer when measuring displacements along one of the coordinate axes; in fig. 3 - the same, when carrying out the correction of the output signal values.

The photoelectric converter contains a light source 1, a shadow mask 2 successively installed along the light beam, associated with a moving nuiMCH object, a differential photo camera), connected to the first bridge circuit 4 with a digital voltmeter 5 in the measuring diagonal and into the second bridge circuit 6 measurement with a digital voltmeter 7 in the measuring diagonal, and the switching unit 8.

Shadow mask 2 contains equal first and second transparent sections 9 and 0, made symmetrical with respect to the plane perpendicular to the sensitivity axis of the differential photodetector 3, and having the shape of a right angle} 1. The differential photodetector 3 is made in the form of two photo potentiometers 11 and 12. The first photo potentiometer 11 is optically coupled to the first transparent section 9, the second photopotentiometer 12 is optically connected to the second transparent section 10. Each photo potentiometer 11 and 12 has 13 deposited on a dielectric substrate resistive layers 14 and 15 and collectors 16 and 17, between which are located photoconductive layers 18 and 19. Resistive layer 11 of the first photopotentiometer 1 has pins 20 and 21, and resistive layer 15 of the second photopotentiometer 12 has pins 22 and 2 3

On the photoconductive layers 14 and 15 of the ne |) - and the second photo-potentiometers I and 12, the first and second transparent participants K11 9 and 10 of the thermal mask 2 were projected, respectively, representing light zoply 24 and 25.

The collectors 16 and 17 of the photo-potentiometer 1 of the I 1 and 12 are connected to a voltmeter 5.

The switching unit 8 has two states and ensures the inclusion of each of the two phototherapy devices 11 and 12 of the differential photodetector 3 in one of the arms of the bridge measurement circuit 4. The first photo heat meter 1 1 is included in the bridge circuit 4 measurements as the first working arm, the second potentiometer 12 - as the second working arm.

0

0

five

0

five

0

five

0

five

In the first state, the output 21 of the photopotentiometer 11 is connected to the output 22 of the photopotentiometer-12 (Fig. 2). In the second state, the output 21 of the photopotentiometer 11 is connected to the output 23 of the photo potentiometer 12 (Fig. 3). In the second measurement bridge circuit 6, the differential photodetector 3 is permanently connected to the first working arm (Fig. 2 and 3).

The Converter operates as follows.

D. To convert one-coordinate movements of the shadow mask 2 along the sensitivity axis of the differential photodetector 3, the switching unit 8 must be in the first state. In this case, the first and second photo potentiometers 1 and 12 of the differential photodetector are included in the bridge measurement circuit 4 as variable resistors 26 and 27, respectively.

The current through the first photopotentiometer 1 flows from the output 20 through the resistive layer 14 to the point of contact of the light probe 24 on the photoconductive layer 18, from where it passes through the photoconductive bridge to the collector 16, reaches the photoconductive bridge at the point of contact of the light probe 25 to the photoconductive layer 19, enters the resistive layer 15 again, flows to pin 23 and further to bridge circuit 4 of measurement. Thus, a portion of the resistive layer 14 of the first photopotentiometer I from the point of contact of the light probe 24 to the pin 21 and a portion of the resistive layer 15 of the second photon tench gauge 12 from the point of contact of the light probe 25 to the pin 23 turn out to be clamped through relatively low-impedance photoconductive bridges and collectors 15 and 17. With HepeMenj.eHHH shadow mask 2, the length of the shunted portions of the resistive layers 14 and 15 is changed, which leads to a simultaneous multidirectional change by the same amount of resistance 26 and 27 (Fig. 2) and, accordingly GOVERNMENTAL, the output voltage of the bridge circuit 4 measurements.

To determine the presence of relative photoconductivity heterogeneity of the photoconductive layers 18 and 19 under the light probes 24 and 25 and to introduce a correction to the output signal 1H of the signal of the bridge circuit 4 measurement during motion conversion, the switching unit 8 must be in the second STATE. In this state, the readings of the digital voltmeter 7 are not used. During the transition: | yueni light probe does not move.

In this case, the first and second photo potentiometers 11 and 12 are included in the bridge measurement circuit 4 as two variable resistors 26 and 27 (Fig. 3). The shunting of the resistive layer 4 of the first photopotentiometer 11 is carried out ana. sooooo Resistive with. yu

15 of the second photopotentiometer 12 is shunted from the point of contact of the light probe

25 on the photoconductive layer 19 to the pin 22. When the shadow mask 2 is interleaved, the length of the shunted portions of the resistive layers 14 and 15 changes, which leads to a simultaneous one-to-one change;

26 and 27. In this case, the symmetry coefficient of the bridge circuit 4 will remain the same as in the first position of the switching unit 8. If the value of the output voltage of the voltmeter 5 changes, this indicates the presence of relative non-uniformity of photoconductivity. Nonuniform photoconductivity within the widths of the probe regions 24 and 25 leads to mismatches between the geometric and electrical centers of the probe.

This is manifested through a change in the relative resistances of the working arms of the bridge circuit.

L, AR / R,

where DC is the part of the resistance of the resistive layer, concluded between the geometric and electric centers of the probe; R is the resistance of the resistive layer.

In order to completely eliminate the influence of errors on the final measurement result, at least three equations must be simultaneously implemented that relate the unknowns D2 to D2 and the input value x (t). The input value is relative. The change in resistance of the shoulders of the bridge circuit

KlEof x (t)

Considering the operating mode of the measuring converter, which corresponds to the power supply of the bridge circuit from the voltage source and the operation of the circuit with a large input resistance, we have the following conversion function:

willows

Up (e.i + k-2)

(P + 1) (P + 1 + P8, -e2)

0

five

W; - readings of uiuppoBoro of co.

R - KOEFTsNS g OHNiMCrpUn SUS)

schemes 4 and: sh..reni.

The ipoo6pa function: u) r aiiHH bridging): Mhi 6 measuring the first state of the tactile block 8 corresponds to the transformation of a bridge circuit with one working arm, Magnitude per t-1) to the auth,: :( 1 due to one-way | The same displacement of probes by the same magnitude. The relative change in the resistance of the working p) arm is equal to Ai A.

As follows from (1) UP2 dI - AJ

 - P24-1 P2 + l + FT (Z7 ----- Ai) (3)

which is equivalent to the equation

l, (I - A2

thirty

20 where u2 is a digital display of a voltmotor; Pj is the coefficient C: the measure of bridge measurement circuit 6;

Y ";

The transformation function of the bridge circuit 4 measurement in the second state KONU of the mutation block 8 corresponds to the bridge circuit with the working arms following the bridge.):; - the corrected translation: zoil. The relative ii3Mei-ieiiue of the resistance of the ncpi -orn of the working arm is equal to Ai, and vgo | 1o; p1 .l-.

As follows from (i

UP,

25

35

PI + PH-I

Where

KM - digital readings of 7, which is equivalent to 15.1)

40

(1- -Р | У «;) (l + У jVtli V:

 and

Where

food

where and ,, - voltage source

the bridge circuit; As a result of solving the system of bridges, the symmetry coefficient of the bridge; (2), (4), (6) was obtained

, f- - relative changes of resistance

nle of the bridge circuit under e (2-f by the action of the input value x (t) j Linux is nanometric in the measuring diagonal of the bridge circuit. As follows from expression (1), in the first state of the switching unit 8 50, the bridge conversion function 4p. schemes (p, a i -y, ((p. Ci-i) v. I

y,

and

Рз (Рз + 1) о1 (2 + 1)

equivalent to linear algebraic

to the equation

 1 - y.R,) n + (1 + yv.) F2 + (1 - R, ym |) l I +

+ () A2 (1 + P |), (2) which at. I eqnvalentny vygde (- P2 p; 55 razhenpyu

PI + I V ,, 2 + V., - m.jy: 4 ,.

y.v ,,

and

i: - and and - 5

four,

, ((

y,

and

Рз (Рз + 1) о1 (2 + 1)

, 2 + V., - m.jy: i: - and and - 5

four,

  R:: (1 Н-1) У2 - и1

TjiKnM image, Photostreaming transmission: - 11 and 12 iomegroids of differential photodetector 3 into bridge circuits 4 and 6 allow comparing their characteristics and taking into account relative inhomogeneities at the moment of transformation of shadow mask position 2.

Claims (1)

Invention Formula A photoelectric displacement transducer containing a light source, a shadow mask with the first and second equal-sized transparent sections and a differential photoreceiver, the first bridge measurement circuit, the switching unit, the transparent parts of the shadow mask mounted along the light flux, are symmetrically relative to the plane perpendicular to the axis of sensitivity of the differential photo1 ; 1 compiler, r ii :: i: r :: ..., chtg), c;. ,,: -: iH) Bi) TO -iiioci and: .. 1l: (M) en1-1Y, it is supplied with rropoi i bridge measurement, start the first worker — o p; 1 the first bridge circuit is connected with the start of the working the shoulder of the second bridge circuit, the ends of the second operating arm of the first bridge circuit and the measuring shoulder of the second bridge adjacent the operating arm are combined; the differential photoreceiver is made of the first and second photopotentiometers, which are included in two adjacent working arms of the first bridge measurement circuit as variable resistors, second The bridge circuit has one working arm, in which a differential photodetector is included, the switching unit is intended for alternately switching to the second operating point. echo first bridge circuit measuring a second potentiometer so that the measuring diagonal of the second bridge circuit connected to the first measurement or the second terminals of the second fotopotentsiometra.