RU2499997C2 - Bridge meter of parameters of dipoles - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: bridge meter of dipole parameters comprises serially connected generator, bridge circuit and zero indicator. The first output of the generator is connected to the inlet of the four-arm bridge circuit, which forms a common outlet of two parallel connected branches of the bridge, the first branch is formed by serially connected two terminals for connection of dipoles of measurement objects and a single resistor of the first arm of the bridge circuit ratio, the first terminal is connected to the first outlet of the pulse generator. The object of measurement comprises serially connected the first resistor and an inductance coil, in parallel to which the capacitor is switched, and the second resistor is connected in series with the three-element circuit. The free output of the single resistor is grounded, and the common output from it and the second terminal for connection of objects of measurement forms the first output of the bridge outlet. The second branch of the bridge is formed by serially connected single capacitor of the second arm of the bridge ratio and dipole of balance elements of the bridge circuit, comprising serially connected first capacitor, first resistor and inductance coil, in parallel to which there is the second resistor connected, the free output of the single capacitor is connected to the first outlet of the generator, the free common output of the inductance coil and the second resistor is grounded, the common output of the single capacitor and the dipole of bridge balancing elements forms the second output of the bridge outlet. Besides, the device comprises an additional capacitor and an additional resistor. The additional capacitor is connected between the second output of the bridge outlet and "earth", and the additional resistor - between the common output of the first capacitor and the first resistor of the second branch of the bridge and "earth".

EFFECT: reduced error of measurement.

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Description

The invention relates to instrumentation, automation and pro-electronics. In particular, it allows you to determine the parameters of four-element bipolar or sensor parameters with a four-element equivalent circuit.

A well-known bridge meter of the parameters of multi-element passive two-pole (AS USSR No. 1247762, G01R 17/10. BI No. 28, 1986), containing a series-connected pulse generator with voltage change over their duration according to the law of power functions, four-arm bridge circuit and zero indicator.

Its disadvantage is the increase in measurement error due to the component error from parasitic capacitances that form ungrounded adjustable balancing elements relative to the "ground". In the indicated meter, in principle, it is impossible to ground all the adjustable balancing elements, therefore the aforementioned stray capacitances and the corresponding component of the measurement error are necessarily present here. From the instability of parasitic capacities, an additional error component also arises, since they change significantly over time (from aging) and especially strongly with temperature. Non-grounded adjustable balancing elements are more strongly affected by electrical noise and interference. In addition, to reduce the harmful effects of external electromagnetic fields and pickups, the balancing elements are often shielded, then in the case of non-earthing of these elements, the question arises of which top of the electric bridge is best to connect the screens. Moreover, each of the available options for connecting screens is not perfect. If these elements are grounded, then it is obvious that the screens should be connected to the ground. In the case of regulation of non-grounded balancing elements by using electronic keys and control electric signals from the control unit, additional difficulties arise and the need to use decoupling elements, for example transformers or optocoupler pairs. With grounded balancing elements, such difficulties are absent. In bridge devices, ceteris paribus prefer bridge circuits with all grounded adjustable balancing elements.

Known bridge meter parameters of the five-element passive two-pole (AS USSR No. 1147986, G01R 17/10. BI No. 12, 1985), containing a series-connected pulse generator with a voltage change over their duration according to the law of power functions, a bridge electrical circuit and zero -indicator.

Its disadvantage is the increase in measurement error due to the component error from parasitic capacitances that form ungrounded adjustable balancing elements relative to the "ground".

The closest in technical essence and the achieved result to the claimed device is a bridge meter of parameters of three-element passive two-terminal devices selected as a prototype (AS USSR No. 945805, G01R 17/10. BI No. 27, 1982), containing a series-connected pulse generator of complex shape , bridge electrical circuit and zero indicator.

Its disadvantage is the increase in measurement error due to the component error from parasitic capacitances that form ungrounded adjustable balancing elements relative to the "ground".

The problem to which the invention is directed is to reduce the measurement error by eliminating the error components from stray capacitances relative to the “ground” of the adjustable balancing elements and the instability of these stray capacitances. These parasitic capacitances are absent, because the meter uses only grounded, adjustable balancing elements.

This is achieved by the fact that in a bridge meter of two-terminal parameters, it contains a supply pulse generator, which consists of pulse shapers with a change in voltage over their duration according to the law K ₀ t ⁰ , K ₁ t ¹ , K ₂ t ² and K ₃ t ³ , where K ₀ , K ₁ , K ₂ and K ₃ are constant coefficients, at is the current time from the switch, from the power amplifier and synchronization unit, the output of each pulse shaper is connected to the corresponding input of the switch, its output is connected to the input of the power amplifier, output which gene forms the first output the pulse generator relative to the ground, the output of the synchronization unit is connected to the input (synchronization input) of each pulse shaper, and its output forms the second output (synchronization output) of the pulse generator relative to the ground, the common bus of the pulse generator is grounded; the first output of the pulse generator is connected to the input of the four-arm bridge circuit, which forms the common output of two parallel connected bridge branches, the first branch is formed by two terminals connected in series for connecting two-terminal measuring objects and a single resistor of the first arm of the bridge circuit relationship, the first terminal is connected to the first output of the pulse generator , the bipolar of the measurement object, in particular, consists of a series-connected first resistor and an inductor, parallel to which in the capacitor is switched on, and a second resistor is connected in series with the three-element circuit, the free output of the single resistor is grounded, and the common terminal of it and the second terminal for connecting two-terminal measuring objects forms the first output terminal of the bridge circuit, the second branch of the bridge circuit is formed by a single capacitor of the second arm of the relationship bridge and bipolar balancing elements of the bridge circuit, consisting of a series-connected first capacitor, the first resistor and coils the inductance ki, in parallel with which the second resistor is connected, the free output of the single capacitor is connected to the first output of the pulse generator, the free common output of the inductor and the second resistor is grounded, the common output of the single capacitor and the two-pole bridge balancing elements forms the second output terminal of the bridge circuit; a null indicator, the first input of which (differential input) is connected to two outputs of the bridge circuit output, its second input (synchronization input) is connected to the second output of the pulse generator, the common bus of the null indicator is grounded, an additional capacitor and an additional resistor are introduced, they are introduced into a two-terminal device with balancing elements of the bridge circuit, an additional capacitor is connected between the second output terminal of the bridge and ground, and an additional resistor is between the common output of the first capacitor and the first resistor the second branch of the bridge and the "ground".

The invention is illustrated in the drawing (Figure 1). The bridge meter of the two-terminal parameters contains a power pulse generator 1, represented by blocks 2-8, which can form a sequence of rectangular, linearly changing, quadratic and cubic pulses. The pulse shaper 2 provides the formation of rectangular pulses, changing according to the law K ₀ t ⁰ ; pulse shaper 3 provides the formation of linearly changing pulses, changing according to the law K ₁ t ¹ ; pulse shaper 4 provides the formation of quadratic pulses, changing according to the law K ₂ t ² ; the pulse shaper provides the formation of cubic pulses that vary according to the law K ₃ t ³ , where K ₀ , K ₁ , K ₂ and K ₃ are constant coefficients, at is the current time. The switch 6 provides a choice of one of four types of pulses generated using pulse shapers 2-5, and then the signal from its output is fed to the input of a power amplifier 7, from the output of which a power-amplified signal is supplied to the first output of the supply pulse generator 1. From the output of synchronization unit 8, the synchronization signal is supplied to the inputs of pulse shapers 2-5, as well as to the second output of the supply pulse generator 1. Generator 1 has two outputs, the first output relative to the ground is the output of the supply signal and connected to the first terminal of the generator bridge diagonal, a grounded generator first output terminal is connected to the second terminal of the generator diagonals, the second pulse generator output is the output synchronization. In the first branch of the bridge circuit, the two-terminal object of the measurement object is connected in series, consisting of the first resistor 9 (R9) and the inductor 10 (L10) connected in series, in parallel with which the capacitor 11 (SI) is connected. In series with the aforementioned three-element circuit, a second resistor 12 (R12) and a single resistor of the first arm of ratio 13 (R13) are connected. In the second branch of the bridge circuit, a single capacitor of the second shoulder of the ratio 14 (C14) and a two-terminal balancing element are sequentially connected. The bipolar of the balancing elements consists of a series-connected first capacitor 15 (C15), a first resistor 16 (R16) and an inductor 17 (L17), in parallel with which a second resistor 18 (R18) is connected. The second capacitance 19 (C19) is connected in parallel with the existing circuit from the first capacitor 15 (C15) connected in series, the first resistor 16 (R16) and the inductor 17 (L17). The third resistor 20 (R20) is connected in parallel to the existing circuit of the series-connected first resistor 16 (R16) and the inductor 17 (L17). The total output of the two-terminal object of measurement and a single capacitor 14 (C14) of the second arm of the ratio forms the first output of the generator diagonal of the bridge circuit. The common output of a single resistor 13 (R13) of the first arm of the ratio and the two-terminal of the balancing elements is grounded and forms the second output of the generator diagonal of the bridge circuit. In the first branch of the bridge circuit, the common output of the two-terminal object of measurement and a single resistor 13 (R13) of the first arm of the relationship forms the first output of the measuring diagonal of the bridge circuit. In the second branch of the bridge circuit, the common output of the single capacitor 14 (C14) of the second shoulder of the ratio and the bipolar of the balancing elements forms the second output of the measuring diagonal of the bridge circuit. The first and second conclusions of the measuring diagonal form, relative to the ground, the differential output of the four-arm bridge circuit, which is connected to the differential input of the zero indicator 21. The common bus of the zero indicator 21 is grounded, and the second input of the zero indicator 21 - the synchronization input is connected to the second output of the generator one.

A bridge meter for the parameters of bipolar operates as follows. In the initial state, the voltages at the input and output of the four-arm bridge circuit are zero. We apply a rectangular pulse train to the bridge from the generator. Under the influence of the next pulse in the steady state, unchanging voltages are established in the branches of the bridge circuit, the difference of which determines the voltage in the measuring diagonal of the bridge circuit (output voltage of the bridge). It depends on the values of capacities 14 (C14), 15 (C15), 19 (C19) and on the values of resistances 9 (R9), 12 (R12), 13 (R13). The first condition for equilibrium of the bridge

$$(C_{\mathrm{fifteen}}+C_{19})R_{13}-C_{\mathrm{fourteen}}(R_9+R_{12})=0(\mathrm{one})$$

By a single adjustment of the value of the grounded capacitor 19 (C19), the flat peak of the pulse nonequilibrium signal is brought to zero, thereby fulfilling the first equilibrium condition of the bridge (1). The equilibrium of the bridge here and hereinafter is indicated by the zero indicator 21 (oscilloscope), while the supply of the synchronization signal from the second output of the generator to the second input of the zero indicator 21 ensures the stability of its readings. Then we feed the pulse train of the ramp voltage to the bridge. When the next such pulse is applied at the bridge output, after the end of the transient process, a pulse nonequilibrium signal with a flat top is established. The second condition for the equilibrium of the bridge

$$\begin{array}{l}{R}_{13}[(C_{\mathrm{fifteen}}+C{}_{19})(R_{16}+R_{\mathrm{twenty}})C_{\mathrm{eleven}}{R}_9+C_{\mathrm{fifteen}}{C}_{19}{R}_{16}{R}_{\mathrm{twenty}}]-\\ C_{\mathrm{fourteen}}[(R_{16}+R_{\mathrm{twenty}})(C_{\mathrm{eleven}}{R}_9{R}_{12}+L_{10})+C_{\mathrm{fifteen}}{R}_{16}{R}_{\mathrm{twenty}}(R_9+R_{12})]=0(2)\end{array}$$

You can perform it by adjusting the resistance of an adjustable grounded resistor 20 (R20). By a single adjustment of the value of this resistor, we bring the flat top of the pulse nonequilibrium signal to zero, i.e. we fulfill the second equilibrium condition (2), while the first condition (1) is not violated, because the parameter 20 (R20) adjustable here is not included in it. After that, we feed a sequence of quadratic pulses to the bridge from the generator. Under the influence of the next pulse, after the end of the transition process, a pulse signal of disequilibrium with a flat top is established at the output of the bridge. The third condition for equilibrium of the bridge

$$\begin{array}{l}(C_{\mathrm{fifteen}}+C{}_{19})C_{\mathrm{eleven}}{R}_{13}[L_{10}(R_{16}+R_{\mathrm{twenty}})+\\ +C_{\mathrm{fifteen}}{C}_{19}{R}_{13}{R}_{\mathrm{twenty}}(C_{\mathrm{eleven}}{R}_9{R}_{16}+L_{17})-\end{array}$$

$$\begin{array}{l}-C_{\mathrm{fourteen}}[L_{10}{C}_{\mathrm{eleven}}{R}_{12}(R_{16}+R_{\mathrm{twenty}})+L_{17}{C}_{\mathrm{fifteen}}{R}_{\mathrm{twenty}}(R_9+R_{12})+\\ +(C_{\mathrm{eleven}}{R}_9{R}_{12}+L_{10})(C_{\mathrm{fifteen}}{R}_{16}{R}_{\mathrm{twenty}}+L_{17})]=0(3)\end{array}$$

By adjusting the grounded inductance 17 (L17) once, we bring the flat top of the pulse voltage of the nonequilibrium to zero and fulfill the third equilibrium condition (3), while the first two equilibrium conditions (1), (2) are not violated, because the parameter 17 (L17) adjustable here is not included in them. After that, we feed a sequence of cubic pulses to the bridge from the generator. Under the influence of the next pulse, after the end of the transition process, a pulse signal of disequilibrium with a flat top is established at the output of the bridge. The fourth condition for equilibrium of the bridge

$$\begin{array}{l}{C}_{\mathrm{eleven}}\{L_{10}{L}_{17}{C}_{\mathrm{fourteen}}{R}_9(R_{16}+R_{\mathrm{eighteen}}+R_{\mathrm{twenty}})+C_{\mathrm{fifteen}}^{}{C}_{19}{R}_{\mathrm{twenty}}[L_{10}{R}_{13}{R}_{16}{R}_{\mathrm{eighteen}}+\\ +L_{17}{R}_9{R}_{13}(R_{16}+R_{\mathrm{eighteen}})]\}-C_{\mathrm{fourteen}}{C}_{\mathrm{fifteen}}{R}_{\mathrm{twenty}}[L_{10}{C}_{\mathrm{eleven}}{R}_{12}{R}_{16}{R}_{\mathrm{eighteen}}+\\ +L_{17}(C_{\mathrm{eleven}}{R}_9{R}_{12}+L_{10})(R_{16}+R_{\mathrm{eighteen}})]=0(\mathrm{four})\end{array}$$

By adjusting the resistance of the adjustable resistor 18 (R18) once, we bring the flat peak of the impulse voltage of disequilibrium to zero and fulfill the fourth equilibrium condition (4), while the first three equilibrium conditions (1) - (3) are not violated, because the parameter 18 (R18) regulated here is not included in them.

From the above it follows that the bridge circuit (Figure 1) has the property of a separate dependent balancing, and balancing should be carried out in the above sequence 19 (C19), 20 (R20), 17 (L17), 18 (R18). Of the four equations [four equilibrium conditions (1) - (4)], the required four parameters are counted: 9 (R9), 10 (L10), 11 (C11), 12 (R12). The values of the parameters of the elements 13 (R13), 14 (C14), 15 (C15), 16 (R16) are constant and known. All adjustable balancing elements - 19 (C19), 20 (R20), 17 (L17), 18 (R18) are grounded. The values of their parameters are known.

Thus, this bridge meter of the two-terminal parameters allows for the separate balancing of the bridge circuit when performing single adjustments of the values of the balancing parameters, which simplifies and accelerates the measurement. All adjustable balancing elements are grounded, which eliminates component errors from spurious capacitances of ungrounded balancing elements of the bridge circuit and from the instability of these parasitic capacitances.

Claims (1)

A bridge meter of two-terminal parameters, containing a power pulse generator, which consists of pulse shapers with voltage changes over their duration according to the law K ₀ t ⁰ , K ₁ t ¹ , K ₂ t ² and K ₃ t ³ , where K ₀ , K ₁ , K ₂ and K ₃ are constant coefficients, and t is the current time from the switch, from the power amplifier and synchronization unit, the output of each pulse shaper is connected to the corresponding input of the switch, its output is connected to the input of the power amplifier, the output of which forms the first output of the generator impulses carry As for the ground, the output of the synchronization unit is connected to the input (synchronization input) of each pulse shaper, and its output forms the second output (synchronization output) of the pulse generator relative to the ground, the common bus of the pulse generator is grounded; the first output of the pulse generator is connected to the input of the four-arm bridge circuit, which forms the common output of two parallel connected bridge branches, the first branch is formed by two terminals connected in series for connecting two-terminal measuring objects and a single resistor of the first arm of the bridge circuit relationship, the first terminal is connected to the first output of the pulse generator , the bipolar of the measurement object, in particular, consists of a series-connected first resistor and an inductor, parallel to which in the capacitor is switched on, and a second resistor is connected in series with the three-element circuit, the free output of the single resistor is grounded, and the common terminal of it and the second terminal for connecting two-terminal measuring objects forms the first output terminal of the bridge circuit, the second branch of the bridge circuit is formed by a single capacitor of the second arm of the relationship bridge and bipolar balancing elements of the bridge circuit, consisting of a series-connected first capacitor, the first resistor and coils the inductance ki, in parallel with which the second resistor is connected, the free output of the single capacitor is connected to the first output of the pulse generator, the free common output of the inductor and the second resistor is grounded, the common output of the single capacitor and the two-pole bridge balancing elements forms the second output terminal of the bridge circuit; a null indicator, the first input of which (differential input) is connected to two outputs of the bridge circuit output, its second input (synchronization input) is connected to the second output of the pulse generator, the common bus of the null indicator is grounded, characterized in that an additional capacitor and additional resistor are introduced , they are inserted into a two-terminal network with balancing elements of the bridge circuit, an additional capacitor is connected between the second output terminal of the bridge and the ground, and an additional resistor is between the common output of the first condensate and the first resistor and the second branch of the bridge and "earth".