SU1525592A1 - Device for measuring electric quantities - Google Patents

Abstract

The invention relates to an electrical measurement technique, namely to precise laboratory-type methods and devices for measuring currents and voltages and the electrical quantities applied to them. The purpose of the invention is to increase accuracy and speed. During the measurement, the reciprocal force effect of the measured electrical value and the reference mechanical quantity on the sensing element 1, equipped with electric circuits 6 and 7, load-receiving cup 14 for the model weight 15, elastic suspension 2 in the form of levers 3 and 4 of the second kind is used. The sensing element 1 is connected to a tracking system with a control amplifier 18, an integrating amplifier 19, and a pulse width modulation circuit for the reference current. The latter includes a comparator 35, a saw-tooth voltage generator 36, frequency dividers 38 and 39, a reference frequency generator 37, a reference current source 32, a correction block 33, a buffer block 31, a key 30. The measurement result is recorded by a pulse counter 40 and is displayed on the reference block 41. A correction block 42 is inserted to eliminate the influence of the own mass of the sensing element 1 on the measurement result. 3 hp f-ly, 5 ill.

Description

buffer unit 31, key 30. The measurement result is recorded by the pulse counter AO and is displayed on the reading unit 41. Correction unit 42 is inserted to eliminate the influence of the own mass of the sensing element 1 on the measurement result. 3 з, п.ф-л, 5 Il.

The invention relates to electrical measuring equipment, namely, to accurate methods and devices for measuring currents and voltages, as well as other electrical quantities, applied to them.

The aim of the invention is to improve accuracy and speed.

FIG. 1 is a schematic of the device for measuring electrical quantities; FIGS. 2 and 3 are variants of the execution schemes with rotation of the sensing element in FIG. 4 and 5 are variants of the schemes with the supply of the measured electrical value and the compensation current of the electric power balance system into one common circuit of the sensitive element and with its turn through 90.

The device (Fig. 1) contains a sensitive epement (SE) 1, made movable and installed through an elastic suspension 2 of parallelogram type in the form of levers 3 and 4 of the second kind, mounted on the base 5. The sensitive element 1 is equipped with two electrical circuits 6 and 7, rigidly mechanically connected with it, and a common magneto-electric inverter 8 with magnet 9 and rm 10, in coaxial gap 11 of which the contours 6 and 7 are evenly spaced, equipped with current leads 12 and 13. CHE 1, in addition , with loaded with a receiving plate 14 for an exemplary weight 15 and a pointer 16 of a noncompensator 17 that reacts to the working displacement dx of the sensitive element 1 and emits an electrical uncompensated signal and connects to the inputs of the control amplifier 18, an integrating amplifier (RI) 19, working separately or together with the first , moreover, regulating and integrating amplifiers 18 and 19 produce compensation currents I c or 1., depending on the operating mode of the sensitive element 1.

In order for the elastic suspension to work properly, 2 shoulders C, 1, 1 ,,, 1 are selected in pairs equal to 1,

H 14 Measured electrical signal

 in the form of current 1 from a source of 20 s

electromotive force E with internal impedance 21 (Zg) is connected via terminals 22 and switch 23.

At mutually perpendicular shots 24 and 25 of base 5 at 90 degrees relative to each other, two meters 26 and 27, for example, of the air-liquid type, are installed, which determine the levels of the sensing element 1.

Electric circuit 6 through current leads 12 and adder 28 is connected to integrator 29, to which via key 30 and buffer unit 31 from reference current source 32, supplied

The correction unit 33 supplies the total value of the reference current -tfl (, „. The non-compensation converter 17 is connected to the input of the electro-balancing equilibrium unit. The control amplifier 18 and the integrating amplifier 19, the adder 28, the integrator 29 together with the pulse-width modulator 34 form the electric power unit0 Go uraanovevani.

In the pulse-width modulator 34, in addition to the key 30, the buffer unit 31 of the current source source 32, and the correction unit 33, a comparator is included

5 35, sawtooth voltage generator 36, reference frequency generator 37 and frequency dividers 38 and 39 with division factors K and K, Comparator 35 inputs are connected respectively to outputs of integrator 29 and sawtooth voltage generator 36, the input of which is connected via divider 38 to the output of the generator 37 reference frequency, the second output

j of which is connected via frequency divider 39 to the second output of the mnpoTito- pulse modulator 34 and to the counting input of the counter 40, the reset input of which is connected to the third output

51

The pulse-width modulator 34, KOTopbDi is connected to the output of the comi-arator 35, the output of the counter 40 is connected to the input of the counting unit 41.

The counter 40 performs with the frequency fgp / Kj the counting of the impulses set by the time interval ut from the comparator 35 and outputs the countdown value of their number N to the reading unit 41. The preset input of the counter 40 is connected to the output of the correction unit 42 with the reset button 43. An EDCE 1 source 44 with an impedance of 45, equal to Z |, is (see Fig. E and 5) the equivalent of the equalization system on the basis of the regulating amplifier 18 and the integrating amplifier 19.

Measurements are carried out as follows.

On an elastic suspension 2 parallel-frame-type in the form of levers 3 n 4 of the second kind, a sensitive element 1 is installed with two electric circuits 6 and 7 and with a common magneto-electric inverter 8, the sensory element 1 is negatively connected with electric power p-1 operation by means of the first electric circuit 6 with the help of the device, -1zо: 1ltel 1 7 uncompensated and the regulating amplifier 18, and also makes an exhibition of the level of the sensing element 1 according to the level gauge 26. In this case, the sensing element 1 works as a static balancing system with a small residual noncompensation 4 Ll of creating astatism of the system in terms of displacement, i.e. receiving Dx O, additionally to the regulating amplifier 18, connect an integrating amplifier 19 to the negative feedback circuit, while the sensitive element 1 is strictly fixed in the same zone of the magnetoelectric inverse converter 8, where the values of induction in its coaxial gap 11 are constant.

Next, check the starting point of the sensing element 1 by the value of the initial compensation current I, which is proportional to the weight P ,, the intrinsic mass m CHE 1 (i.e., taking into account the load-receiving mass of the cup 14, electrical circuits 6 and 7, levers 3 and 4, and also suspension 2). At the same time, the current value is fixed (for

commemorated). When using the method of width-impulse)) SNY module 1p1I check the starting point but TOKV I

is produced in the following way: the current - 1, coming through 28, together with the counter current 1 (, "from the reference current source 32 - to the integrator 29, whose output signal

is compared with comparator 35 with sawtooth voltage generator 36. , the change in the duty cycle of the pulses ts ka L,. Therefore, ipfina ipp lsov gokl If.r,., T, e. time at

of which 30 remains open and sc ;; tg: 40 40% of the total clock count of impulses h ;; co1-1Y f., r / 1, pronoglu- ninal to the number of 1, ta1-; iMnynbtoB N, fic: readable by block 41

Opera gfi: g 1g h; h; layer of N pulses, pr (: portion of the main current I-1., And weight P, s; s1: gtvennoy mass of the element FJCTKUTe.niJthix, assembled. For; -sk :) rheni hp pO value of the following u: l) e1: 1lite 11th operations initial h); ac en1; e K l pulses are reset to zero: by pressing the reset button 43 of the iiOKrisaHHiT ;; inclusions p2 KOjipcMin; - ;. L etG.-1 c / i - iae CKopp -7T5: poraiMipp jriaMt-iHiie of the source p.-IBS o zero (, N, - 0),

Next, set the raHiiBJinBawr to the load-receiving cup 14 °; - -yr; pike weight 15 required i :: ca Р, - iMncrw m, where g, is the acceleration of free g

falls), for example, U) 0 g, and they are defined illogically .sun} .g near the current 1., equilibrium; weight 1 :, according to the number of pulses Npg, recorded by a repetitive block of 41, after which they are found to be large

NO K ,,. Gm ,, 5. (1)

If the scaling coefficient K, which depends mainly on the magnetic B in the gap 11, has not changed since the previous graduation, then using the method

Ip pulse modulus Ip: and the adjustment of the level of the arresting current It, n is not made. In the case of a change in the scale of the coefficient K, i.e. the deviation from the predetermined number of a known number, for example, due to a change in the ambient temperature, the level 1p is adjusted. by filing from the correction unit 33 an additional current L1p5.

Then, after several cycles of checking the starting point and the scale factor K, samples of the weight 15 from the cup 14 are removed and the measured electrical value 1 is introduced into the second electric circuit 7 by closing the switch 23, thus creating an imbalance of the sensing element 1 by the value lx, which is working on current 1c. The current I 1 ,, is measured, ak and earlier by the method of pulse-width modulation and is counted by a counting block 41 in the form of the number of pulses N., by the formula

N. K, 1,

(2)

where K is the scale coefficient (4), the patient, determined by the number of turns of electric circuits 6 and 7, induction B in the gap 11, design dimensions of electric circuits 6 and 7, frequency Fjjf, reference frequency generator 37, and division factor K of divider 39 frequencies.

Since in the proposed method, the accuracy of maintaining the scales of K and K is checked very quickly and at any time to the exact extent of the sample 15, which has greater temporal stability and accuracy, and the accuracy of maintaining the reference frequency using a reference oscillator 37 on a quartz crystal. Since the resonator is also large, the device allows the measurement of electrical quantities with an error of no more than 0.001-0.003%.

In addition to the main one, the following measurement variant is possible, increasing 1; its accuracy (see Fig. 2 and 3). After fixing the constant K, and removing the model weight 15, the sensitive element 1 is rotated 90 ° in the direction of the weight RD of its own weight: perpendicular to: the working displacement ml of its sensitive element 21 and the indicator 16, the display of the sensitive level element 1 according to the gauge 27 level based on 5, then the measured value 1 is introduced into the electric circuit 7.

In this case, the effect of weight P in general does not displace the sensitive element 1 and the decree

16, and the value of the initial compensation current tends to zero, and with a balanced sensitive element 1, it is zero, 0. In this case, the additional heating of the sensitive element 1 by current I does not occur and the measurement accuracy of 1 increases.

In addition, it is possible to carry out measurements (see Figs. 4 and 5), when the measured electrical quantity I is introduced into the same common electric circuit 6 of the sensitive element 1, which has a lower impedance Z compared to impedance 2 and Zj source 44 and source 20 of the measured signal 1,,;

. In this case, after checking and adjusting the initial point of the sensitive element 1, as well as fixing the constant K

TP

the measured signal 1 is introduced into the electric circuit 6, and since, to achieve a power balance, the currents 1 and 1 must be equal, the resulting current is zero.

five

O 0

0

five

CH x Oh, and the heating of the sensitive element currents I and I does not occur.

This greatly improves the accuracy of measurements. At the same time, with the chosen impedance ratios, the errors 4 1 c, ny1 become minimal.

In addition, when the sensitive element 1 is rotated by 90 (see Fig. 5), the need to feed an initial current into the electric circuit 6 disappears, which also increases the measurement accuracy.

In this case, when the switch 23 is open and the model weight 15 is not present on the load-receiving cup 14, the sensitive element 1 is displaced downward by distance x x under the influence of the weight PO of its own weight.

In this case, the pointer 16 is moved relative to the non-compensating converter 17, which produces a non-compensating signal L L g coming to the control amplifier 18 and the integrating lean amplifier 19, where it is amplified and integrated, and then supplied as current I. in the electric circuit 6 and creates a force F about PO) providing D x 0.

Next, the current 1 after the electric circuit 6 together with the countercurrent compensation current I; ,,, flows through the adder 28 into the integrator 29, comparing them in time. The output signal of the integrator is fed to the first input of the comparator 35, the second input of which is supplied by r generator; - torus 36 sawtooth voltage linearly increasing voltage.

At the moment of equality of the signal of the integrator 29 and the voltage from the sawtooth voltage generator 36, the comparator 35 is activated and gives commands to turn off the key 30 and stop the counting of pulses on the counter 40, into which they go B during the time interval ut from the reference frequency generator through the frequency divider 39 .

On the readout block 41, the number of pulses Np, proportional to the value P., is highlighted.

To simplify the last steps, pressing the reset button 43 is performed by means of a correction block 42 (by storing these readings, for example, and automatically subtracting them in a clock) setting the counter 40 points to the zero position on the reading block 41, t. e. getting NO 0. I

Next, an exemplary weight 15 of the required mass is installed on the load-carrying cup 14 and the scale factor K is fixed according to equation (1). If necessary, the Ion level is adjusted by adding a second token correction from the block 33. the starting point of the sensing element 1 and the coefficient K, and finally turn on the switch 23 and enter the measurement eBx

The largest electric signal, whose rank is counted by the counting unit.

Claims (4)

1. A device for measuring electrical quantities, comprising a sensitive element, a suspension, a base, a non-compensation converter, the output of which is connected to the input of an electric power balance unit, the output of which is connected to the input of the first electric circuit, the reading unit, ten 1.5 20 25 thirty 35 40 - 45 50 55 This is due to the fact that, in order to increase accuracy and speed, a second electric circuit, a magnetoelectric inverter, a counter, a correction unit, a sensitive element, are made in the form of two levers of the second kind, mounted on a parallelogram type suspension and an automatic connected to two electrical circuits placed in the gap of the magneto-electric; tric invertor, the input of the second electric KCH .ypa is connected to the input terminal of the MI device; It comprises a control amplifier whose input is connected to the input electric power unit nopesh11vani uranium, I1 tegriruyupr1y amplifier, with m - 1mator integrator, and 1- 1Sh1rotio-pulse modulator output regularity. Through the integrating service amplifier, it is connected to the first output of the first electric circuit, the second output of which is connected to the first input cv MMaTopa, the second input of which is connected to the first output of the pulse-width modulator, the input of which through the integrator is connected to the input 1Sh1rottoimpul1, modulator, the second and third outputs of which are connected respectively to the counting input and the reset input of the counter, whose preset input is connected to the output of the correction unit, and the output from the getch is connected to the input unit. 2. The device according to claim 3, wherein the pulse-width modulator comprises a comparator, a sawtooth generator, a reference frequency generator, two frequency dividers, a reference current source, a correction unit, a buffer block, and a key The first input of the comparator is connected to the input of the pulse-width modulator, the second input of the comparator is connected to the output of the sawtooth generator, the input of which is connected through the first divider to the output of the reference frequency generator, which through the second divider is connected to the BToptiM output th pulse-width modulator, whose third output is connected to the comparator output and controls w: Dim key through which pervsh GOVERNMENTAL (xq pulse width modulation torus soe11 dinene with the output of the buffer unit, whose input is connected to the outputs of the reference current source and the correction unit. 3. A device according to claim 3, characterized in that, on the basis of two levels of position of the sensitive element, which are oriented mutually perpendicular, are fixed. 23./ .. Fig 152559212 4. The device according to claim 3, characterized in that the first and The second electric circuits are made in the form of a coil with a single winding, the impedance value of which is chosen to be lower than the impedances of the electric power balancing unit and the source of the measured electrical signal. 7K 7 5 f I Ihx Fi.Z IK + L1) ( 2B 27 Ex phi9.5