RU2661457C1 - Bridge measuring device for measuring parameters of two-terminal circuits - Google Patents

Abstract

FIELD: monitoring and measurement equipment.

SUBSTANCE: invention relates to instrumentation, automation and industrial electronics and can be used to monitor and determine the parameters of measurement objects, as well as physical quantities through parametric sensors. Bridge measuring device for measuring parameters of the two-terminal circuits comprises a series-connected pulse generator with voltage variation according to the law of step functions, the bridge electrical circuit and the zero indicator. To achieve the technical result, an additional resistor is introduced and the connection of the elements is changed. Additional resistor is connected to the first terminal for connection of the two-terminal circuits and measuring objects, which is connected to the common terminal of a single resistor in the second branch of the bridge circuit and the two-terminal circuit of the first, second resistors and inductive coil. Second terminal for connecting the two-terminal circuits of the measuring objects is grounded. Two-terminal circuit of a parallel-connected capacitor and a resistor is connected between the free terminal of the additional resistor and the second terminal for connecting the two-terminal circuit of the measurement objects. Combination of the additional resistor, the capacitor and the resistor of the two-element circuit form a two-terminal circuit of the measurement object.

EFFECT: reduction of the measurement error due to the elimination of the error component from the parasitic capacitance relative to the "earth" of the ungrounded multi-element two-terminal circuit, as well as the instability of this parasitic capacitance through the use of only grounded multi-element two-terminal circuits.

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Description

The invention relates to instrumentation, automation and industrial electronics and can be used to control and determine the parameters of measurement objects, as well as physical quantities by means of parametric sensors.

Known bridge meter parameters of multi-element passive two-terminal [USSR AS No. 1157467, G01R. Bridge meter parameters of multi-element passive two-terminal / G.I. Peredelsky. - Publ. in bull. No. 19, 1985], containing a series-connected pulse generator with voltage changes over their duration according to the law of steppe functions, a four-arm bridge circuit and a zero indicator.

Its disadvantage is the inability to ground both existing multi-element bipolar. All things being equal, in practice, preference is given to bridge circuits, where all available multi-element bipolar terminals are grounded. An ungrounded multi-element bipolar forms a parasitic capacitance relative to the ground, which causes a corresponding additional component of the measurement error due to this parasitic capacitance. In addition, this parasitic capacitance is unstable and, as is known, varies significantly over time and especially with temperature. In the particular case of an ungrounded bipolar with adjustable balancing elements and using the same-type elements matrix, controlled keys and control and matching circuits, it is necessary to use additional decoupling elements - transformers or optocoupler pairs. Changing the value of the balancing parameter is carried out here by closing and opening the keys under the action of signals from a grounded electronic control circuit. If the balancing element is grounded, then no additional decoupling elements are required. Also, in the particular case of an ungrounded two-terminal object of measurement and the use of a sensor with a communication line, interference signals are induced on the latter and cause a corresponding additional component of the measurement error, since here the communication line is also ungrounded. A sensor or sensor together with a communication line is a multi-element equivalent circuit. If the measurement object is grounded, then the interference signals and the corresponding component of the measurement error are significantly less, since the communication line is grounded. An ungrounded communication line also has a parasitic capacitance relative to the ground. It can be noted that it is basically impossible to ground both multi-element bipolar in the bridges of Schering, Maxwell, Hay, Anderson, Ilyuvisi [Koltsov A.A. Balancing circuitry. -: Energy, 1976, 272 pp., Figures 4-7 a, b and f (p. 119), 4-8 b and d (p. 123), respectively].

The closest in technical essence and the achieved result to the claimed device is selected as a prototype bridge meter parameters of the three-element passive two-terminal [AS USSR No. 798607, G01R. Bridge meter of parameters of three-element passive two-terminal / G.I. Peredelsky. - Publ. in bull. No. 3, 1981]. The bridge meter contains a series-connected pulse generator of complex shape, a four-arm bridge electrical circuit and a zero indicator.

Its disadvantage is the inability to ground both existing multi-element bipolar.

The problem to which the invention is directed is to reduce the measurement error by eliminating the component error from the parasitic capacitance relative to the “ground” of the ungrounded multi-element bipolar, as well as the instability of this parasitic capacitance due to the use of only grounded multi-element bipolar.

This is achieved by the fact that in the bridge meter of two-terminal parameters containing a supply pulse generator, consisting of a synchronization cascade, shapers of rectangular, linearly varying and quadratic pulses, a switch and a power amplifier, the output of the synchronization cascade is connected to each input of the available three pulse shapers, the outputs of which connected to the inputs of the switch, the output of which is connected to the input of the power amplifier, the output of the power amplifier forms the first output of the generator power pulses relative to the "ground", the second output of the power pulse generator - the synchronization output forms the output of the synchronization stage, the common bus of the power pulse generator is grounded, the first output of the power pulse generator is connected to the generator diagonal of the four-arm bridge circuit (with the bridge input), which consists of two parallel included branches, the first of them consists of two series-connected resistors, the free output of one of them is connected to the first output of the supply pulse generator, and one terminal of the other resistor is grounded, the common terminal of the two resistors forms the first output terminal of the four-arm bridge circuit, the second branch of the four-arm bridge circuit consists of a series-connected single resistor and a two-terminal circuit from the first resistor and an inductor connected in series, the second resistor is connected in parallel with the last, the common terminal of a single resistor and the two-terminal forms the second output terminal of the four-arm bridge circuit, also in the four-arm bridge circuit there is a two-element chain a capacitor and a resistor; two conclusions of the four-arm bridge circuit are connected to the differential (first) input of the null indicator, its other input, the synchronization input, is connected to the second output of the supply pulse generator, the common bus of the null indicator is grounded, an additional resistor is introduced and the connection of elements is changed, an additional resistor is connected to the first a terminal for connecting two-terminal measuring objects, which is connected to a common output of a single resistor in the second branch of the bridge circuit and a two-terminal from the first, second resistors and inductor active coil, the second terminal for connecting two-pole measuring objects is grounded, the two-element circuit from the capacitor and resistor is transferred from the first branch of the bridge circuit to the second branch, the elements are connected to each other in parallel and this two-element circuit is connected between the free terminal of the additional resistor and the second terminal for connecting two-terminal objects of measurement, the combination of an additional resistor, a capacitor and a two-element circuit resistor form a two-terminal object of measurement.

The invention is illustrated in the drawing (Figure 1).

формирователя 3 линейно изменяющихся импульсов $$(K_1{t}^1),$$

формирователя 4 квадратичных импульсов $$(K_2{t}^2),$$

где $$K_0,K_1$$

и $$K_2$$

− постоянные коэффициенты, t − текущее время, усилителя 5 мощности, коммутатора 6 и каскада 7 синхронизации. Выход каскада 7 синхронизации соединён с каждым входом формирователей прямоугольных, линейно изменяющихся и квадратичных импульсов, выходы которых подключены к коммутатору 6. Выход коммутатора 6 соединён с входом усилителя 5 мощности. Выход усилителя 5 мощности образует первый выход генератора 1питающих импульсов относительно «земли». Второй выход генератора 1 питающих импульсов - выход синхронизации образует выход каскада 7 синхронизации. Общая шина генератора 1 питающих импульсов заземлена. Первый выход генератора 1 импульсов соединён с генераторной диагональю четырёхплечей мостовой цепи (с входом моста), которая состоит из двух параллельно включенных ветвей. Первая ветвь четырёхплечей мостовой цепи образована двумя соединёнными последовательно резисторами 8 (R8) и 9 (R9). Свободный вывод резистора R8 соединен с первым выходом генератора 1 питающих импульсов. Свободный вывод резистора R9 заземлен. Общий вывод резисторов R8 и R9 образует первый вывод выхода (первую вершину измерительной диагонали) четырехплечей мостовой цепи. Вторая ветвь четырехплечей мостовой цепи состоит из последовательно соединённых одиночного резистора 10 (R10) и двухполюсника составленного из включенных последовательно первого резистора 11 (R11) и индуктивной катушки 12 (L12), параллельно которой включен второй резистор 13 (R13).The bridge meter of the two-terminal parameters contains a generator 1 of supply pulses, consisting of a shaper 2 of rectangular pulses $$(K_0{t}^0),$$

shaper 3 linearly changing pulses $$(K_{\mathrm{one}}{t}^{\mathrm{one}}),$$

4 quadratic pulse shaper $$(K_2{t}^2),$$

Where $$K_0,K_{\mathrm{one}}$$

and $$K_2$$

- constant coefficients, t - current time, power amplifier 5, switch 6 and synchronization stage 7. The output of the synchronization stage 7 is connected to each input of the formers of rectangular, ramp and quadratic pulses, the outputs of which are connected to the switch 6. The output of the switch 6 is connected to the input of the power amplifier 5. The output of the power amplifier 5 forms the first output of the supply pulse generator 1 relative to the “ground”. The second output of the generator 1 of the supply pulses - the synchronization output forms the output of the synchronization stage 7. The common bus of the generator 1 of the supply pulses is grounded. The first output of the pulse generator 1 is connected to the generator diagonal of the four-arm bridge circuit (with the input of the bridge), which consists of two branches connected in parallel. The first branch of the four-arm bridge circuit is formed by two resistors 8 (R8) and 9 (R9) connected in series. The free output of the resistor R8 is connected to the first output of the supply pulse generator 1. The free terminal of resistor R9 is grounded. The common output of the resistors R8 and R9 forms the first output pin (the first peak of the measuring diagonal) of the four-arm bridge circuit. The second branch of the four-arm bridge circuit consists of a single resistor 10 (R10) connected in series and a two-terminal circuit composed of the first resistor 11 (R11) connected in series and the inductive coil 12 (L12), in parallel with which the second resistor 13 (R13) is connected.

The common output of a single resistor and a two-terminal network forms the second output terminal of the bridge circuit. The first terminal for connecting the two-terminal objects of measurement is connected to the common output of a single resistor, two-terminal and the second output of the bridge circuit output. The second terminal is grounded. The bipolar of the measurement object is formed by the first 14 (R14) and second 15 (R15) resistors connected in series, the capacitor 16 (R16) is connected in parallel with the last. The free terminal of the resistor 14 is connected to the first terminal for connecting two-terminal measuring objects, and the common terminal of the resistor 15 and capacitor 16 is connected to the second terminal.

Two outputs of the four-arm bridge circuit output are connected to the differential (first) input of the null indicator 17. Another input of the null indicator 17 is a synchronization input connected to the second output of the supply pulse generator 1. The common bus of the zero indicator is connected to the second peak of the generator diagonal of the four-arm bridge circuit and is grounded. In the four-arm bridge circuit, the resistance values of the resistors R8, R9 and R10 are known and constant. The parameters are the resistors R14 and R15 and the capacitor C16, which form the two-terminal device of the measurement object. Adjustable balancing variables are the parameters of the resistors R11 and R13 and the inductive coil L12. The values of their parameters are known.

The work of a bridge measuring device of two-terminal parameters is as follows. Initially, the voltage at the input and output of the four-arm bridge circuit is zero. First of all, a four-arm bridge circuit is fed with a rectangular pulse train. These signals are generated by the square-wave generator 2 in the supply pulse generator 1, and through the switch 6 and the power amplifier 5 they are supplied to the output of the supply pulse generator 1. In the steady state, under the influence of the next pulse of a rectangular shape at the output of the four-arm bridge circuit, an unchanging voltage is established during the time interval from the end of the transition process to the end of the pulse. The flat peak of this nonequilibrium voltage is reduced to zero by a single adjustment of the variable balancing element R11, which ensures the fulfillment of the first equilibrium condition of the four-arm bridge chain

$$A_{\mathrm{one}}=R_9{R}_{10}(R_{\mathrm{eleven}}+R_{\mathrm{fourteen}}+R_{\mathrm{fifteen}})-R_8{R}_{\mathrm{eleven}}(R_{\mathrm{fourteen}}+R_{\mathrm{fifteen}})=0.\text{(one)}$$

Then, the pulse train of a linearly varying voltage acts on the generator diagonal of the four-arm bridge circuit. When another such impulse is exposed, after the end of the transient process, the impulse non-equilibrium signal with a flat top is established in the measuring diagonal of the four-arm bridge circuit. This vertex, taking into account the fulfilled first equilibrium condition (1), is reduced to zero by a single adjustment of the variable balancing element L12. In this case, the second equilibrium condition of the four-arm bridge chain is satisfied

$${\mathrm{BUT}}_2=R_9{R}_{10}[L{}_{12}+C_{16}{R}_{\mathrm{fifteen}}(R_{\mathrm{eleven}}+R_{\mathrm{fourteen}})]-R_8[L_{12}(R_{\mathrm{fourteen}}+R_{\mathrm{fifteen}})+C_{16}{R}_{\mathrm{eleven}}{R}_{\mathrm{fourteen}}{R}_{\mathrm{fifteen}}]=0.\text{(2)}$$

In this case, the fulfillment of the first equilibrium condition (1) is not violated, since this condition does not contain a variable adjustable balancing element L12.

Lastly, through a switch 6 from the generator 1 of the supply pulses, quadratic pulses are fed to the generator diagonal of the four-arm bridge circuit. In its measuring diagonal under the influence of the next such pulse, a pulse nonequilibrium signal is established. This signal after the end of the transition process has a flat top, which under the conditions (1) and (2) is reduced to zero by a single adjustment of the variable balancing element R13. As a result, the third equilibrium condition of the four-arm bridge chain is satisfied

$${\mathrm{BUT}}_3=R_9{R}_{10}(R_{\mathrm{eleven}}+{\mathrm{<figure-callout\; id="13"\; label="R"\; filenames="00000010.png"\; state="\{\{state\}\}">R</figure-callout>}}_{13}+R_{\mathrm{fourteen}})-R_8{R}_{\mathrm{fourteen}}(R_{\mathrm{eleven}}+R_{13})=0.\text{(3)}$$

In this case, the fulfillment of the first (1) and second (2) equilibrium conditions is not violated, since these conditions do not contain a variable adjustable balancing element R13.

The required values of the parameters of the three elements of the two-terminal object of measurement R14, C16 and R15 are determined from the three equilibrium conditions of the four-arm bridge circuit (1) - (3). Therefore, three unknown parameters are found from the solution of three equations.

Thus, the proposed bipolar bridge parameter meter allows to reduce the measurement error by eliminating the component error from the parasitic capacitance relative to the “ground” of the non-earthed multi-element two-terminal device, as well as the instability of this parasitic capacitance due to the use of only grounded multi-element two-terminal devices. Also, in the proposed bridge meter of two-terminal parameters, dependent separate balancing is implemented.

Claims (1)

A bridge two-terminal parameter meter containing a supply pulse generator consisting of a synchronization cascade, rectangular, linearly varying and quadratic pulse shapers, a switch and a power amplifier, the output of the synchronization cascade is connected to each input of three available pulse shapers, the outputs of which are connected to the inputs of the switch, the output which is connected to the input of the power amplifier, the output of the power amplifier forms the first output of the supply pulse generator relative specifically “ground”, the second output of the supply pulse generator — the synchronization output forms the output of the synchronization cascade, the common bus of the supply pulse generator is grounded, the first output of the supply pulse generator is connected to the generator diagonal of the four-arm bridge circuit (with the bridge input), which consists of two branches connected in parallel , the first of them consists of two series-connected resistors, the free output of one of them is connected to the first output of the supply pulse generator, and the free output of the other The ora is grounded, the common terminal of the two resistors forms the first output terminal of the four-arm bridge circuit, the second branch of the four-arm bridge circuit consists of a series-connected single resistor and a two-terminal circuit from series-connected first resistor and an inductor, a second resistor is connected in parallel with the last, the common terminal of a single resistor and a two-terminal circuit the second output terminal of the four-arm bridge circuit, also in the four-arm bridge circuit there is a two-element circuit from the capacitor and a resistor pa; two conclusions of the four-arm bridge circuit are connected to the differential (first) input of the null indicator, its other input, the synchronization input, is connected to the second output of the supply pulse generator, the common bus of the null indicator is grounded, characterized in that an additional resistor is introduced into it and the connection of elements is changed , an additional resistor is connected to the first terminal for connecting two-terminal measuring objects, which is connected to the common output of a single resistor in the second branch of the bridge circuit and the two-terminal from the first of the second, second resistors and inductive coils, the second terminal for connecting the two-terminal measuring objects is grounded, the two-element circuit from the capacitor and resistor is transferred from the first branch of the bridge circuit to the second branch, the elements are connected to each other in parallel and this two-element circuit is connected between the free output of the additional resistor and a second terminal for connecting two-terminal measuring objects, the combination of an additional resistor, a capacitor and a two-element circuit resistor form a two-terminal object of measurement.

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