RU2495442C1 - Bridge measuring device of parameters of bipoles - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: bridge measuring device of parameters of bipoles includes a generator of a feed complex electric signal, a bridge circuit and a null indicator, which are in-series connected. At that, bridge measuring device of parameters of bipoles includes a bipole with balancing elements, which is included in the bridge circuit, an additional resistor that is connected parallel to the first inductance coil in the first branch of the bridge circuit.

EFFECT: reducing measurement error owing to excluding error components from parasitic capacitances relative to earth of adjustable balancing elements and non-stability of those parasitic capacitances.

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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.

Known bridge meter parameters of multi-element passive two-pole (AS USSR No. 1244762 G01R 17/10, BI 1986, No. 28), 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. The values of these parasitic capacities are relatively considerable, because the overall dimensions of exemplary adjustable elements are significantly larger than the overall dimensions of unregulated exemplary elements. 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 event that these elements are not grounded, 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 ungrounded 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 1985, No. 12), containing a series-connected pulse generator with 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 passive two-terminal parameters selected as a prototype (AS USSR No. 1150555 G01R 17/10, BI 1985, No. 14), containing a pulse generator with voltage changing in series the course of their duration according to the law of power functions, a bridge electrical circuit and a 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. The above parasitic capacitances are absent because the meter uses only grounded, adjustable balancing elements.

This is achieved by the fact that in the bridge meter of two-terminal parameters, it contains a supply pulse generator, which consists of pulse shapers with voltage changes over their duration according to the law K ₁ t ¹ , K ₂ t ² , K ₃ t ³ and K ₄ t ⁴ , where K ₁ , K ₂ , K ₃ and K ₄ 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 forms the first output of the gene Ator pulses relative to "earth", sync block output is connected to the input (clock input) of each of the pulse, and its output forms a second output (output synchronization) pulse generator relative to "earth", the total pulse generator bus is grounded; the first output of the pulse generator is connected to the input of the four-arm bridge circuit, which consists of two branches connected in parallel, the first of which includes a single resistor of the first shoulder of the bridge relationship and a two-terminal with elements of balancing the bridge circuit, the free output of a single resistor is connected to the first output of the pulse generator , the free output of a two-terminal with balancing elements is “grounded”, the common output of it and a single resistor forms the first output of the bridge circuit output, a two-terminal device with balancing elements consists of a first inductive coil and a circuit composed of a first resistor and a second inductive coil connected in series, a second resistor connected in parallel, the second branch of the bridge includes a single resistor of the second arm of the bridge relationship and two terminals for connecting the two-terminal object measurement, the free output of a single resistor is connected to the first output of the pulse generator, one of the terminals for connecting a two-pole The measurement object is “grounded”, the common terminal of the other terminal and the single resistor forms the second output terminal of the bridge circuit, the two-terminal circuit of the measurement object, in particular, consists of the first inductive coil and the circuit of the first resistor and second inductive coil connected in parallel to the common terminal of two inductive a second resistor is connected to the coils and this common terminal is connected to a grounded terminal for connecting two-terminal measuring objects; 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 resistor is introduced and the connection of the bridge elements is changed circuit, an additional resistor is connected parallel to the first inductive coil of the first branch of the bridge circuit, the common output of the first inductive coil, additional resistor and the first resistor in the first branch of the bridge is connected to the first with the output of the bridge circuit, the common terminal of the first inductive coil and the first resistor in the second branch of the bridge circuit is connected to an ungrounded terminal for connecting two-terminal measuring objects, the free terminal of the second resistor of the second branch of the bridge is connected to the common terminal of the first resistor and second inductive coil existing in this branch.

The invention is illustrated in the drawing (Figure 1). The bipolar bridge parameter meter contains a supply pulse generator 1, represented by blocks 2-8, which can generate sequences of linearly changing, quadratic, cubic pulses, as well as voltage-changing pulses during their duration according to the law of the fourth degree. The pulse shaper 2 provides the formation of linearly changing pulses, changing according to the law K ₁ t ¹ ; pulse shaper 3 provides the formation of quadratic pulses, changing according to the law K ₂ t ² ; pulse shaper 4 provides the formation of cubic pulses, changing according to the law K ₃ t ³ ; pulse shaper 5 provides the formation of pulses with voltage change over their duration according to the law of the fourth degree, changing according to the law K ₄ t ⁴ , where K ₁ , K ₂ , K ₃ and K ₄ 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 synchronization unit 8, the synchronization signal is fed 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 signals and connected to the first output of the generator diagonal of the bridge, the grounded output of the first output of the generator is connected to the second output of the generator diagonal. The second output of the pulse generator is the synchronization output. In the first branch of the bridge circuit, a single resistor of the first shoulder of the ratio 9 (R9) and a two-terminal with balancing elements, consisting of the first inductive coil 10 (L10) and the circuit of the first resistor 11 (R11) connected in series, and the second inductive coil 12 are connected in series (L12), in parallel with which the second resistor 13 (R13) is connected, and also in parallel with the first inductive coil 10 (L10), the third resistor 14 (R14) is turned on. In the second branch of the bridge circuit, a single resistor of the second arm 15 (R15) and a two-terminal device of the measurement object, consisting, in particular, of a parallel inductance of the first inductive coil 16 (L16) and a circuit of the first resistor 17 (R17) and the second inductive coil 18 (L18), connected to the common terminal of the two inductive coils the second resistor 19 (R19) and this common terminal is connected to a grounded terminal for connecting two-terminal measuring objects. The second terminal of the resistor 19 (R19) is connected to the common terminal of the first resistor 17 (R17) and the second inductive coil 18 (L18). The common terminal of the single resistor 9 (R9) of the first ratio arm and the single resistor 15 (R15) of the second ratio arm forms the first output of the generator diagonal of the bridge circuit. The general output of the two-terminal with balancing elements of the first branch of the bridge and the two-terminal object of the measurement of the second branch of the bridge 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 a single resistor 9 (R9) of the first link arm and a two-terminal with balancing elements forms the first output terminal of the measuring diagonal of the bridge circuit. In the second branch of the bridge circuit, the common terminal of a single resistor 15 (R15) of the second ratio arm and the two-terminal terminal of the measurement object forms the second terminal of the measuring diagonal output 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 20, the common bus of which is grounded, and the second input of the zero indicator 20 - the synchronization input is connected to the second output of the generator 1.

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 sequence of linearly changing pulses to the bridge from the generator of a complex electric signal. When another pulse is applied after the end of the transition process, 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 (bridge output voltage). It depends on the values of inductances 10 (L10), 16 (L16) and on the values of resistances 9 (R9), 15 (R15). The first condition for the equilibrium of the bridge is

$$L_{10}{R}_{\mathrm{fifteen}}-L_{16}{R}_9=0\left(\mathrm{one}\right)$$

By adjusting the inductance value 10 (L10) once, the flat peak of the pulse nonequilibrium signal is reduced 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 20 (oscilloscope), while the supply of the synchronization signal from the second output of the generator to the second input of the zero indicator 20 ensures the stability of its readings.

Next, we feed the bridge with a sequence of quadratic pulses. 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 is

$$R_{\mathrm{eleven}}{R}_{\mathrm{fourteen}}{R}_{\mathrm{fifteen}}-R_9{R}_{17}\left(R_{\mathrm{eleven}}+R_{\mathrm{fourteen}}\right)=0\left(2\right)$$

You can perform it by adjusting the resistance of the resistor 14 (R14). By a single adjustment of the resistance 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 Parameter 14 (R14) adjustable here is not included.

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 third condition for equilibrium of the bridge is

$$L_{12}{R}_{\mathrm{fourteen}}{R}_{\mathrm{fifteen}}-R_9\left[L_{\mathrm{eighteen}}\left(R_{\mathrm{eleven}}+R_{\mathrm{fourteen}}\right)+L_{12}{R}_{17}\right]=0\left(3\right)$$

By adjusting the inductance 12 (L12) once, we bring the flat peak of the impulse voltage of the disequilibrium to zero and fulfill the third equilibrium condition (3), while the first two equilibrium conditions (1), (2) are not violated, because Parameter 12 (L12), adjustable here, is not included in them.

After that, we feed to the bridge from the generator a sequence of pulses with a voltage change over their duration according to the law of the fourth degree. 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 is

$$R_{\mathrm{fourteen}}{R}_{\mathrm{fifteen}}\left(R_{\mathrm{eleven}}+R_{13}\right)-R_9\left(R_{\mathrm{eleven}}+R_{13}+R_{\mathrm{fourteen}}\right)\left(R_{17}+R_{19}\right)=0\left(\mathrm{four}\right)$$

By adjusting the resistance of the resistor 13 (R13) 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 parameter 13 (R13) regulated here is not included in them.

From the above it follows that the bridge circuit (Figure 1) has the property of separate dependent balancing, and balancing should be carried out in the above sequence 10 (L10), 14 (R14), 12 (L12), 13 (R13). Of the four equations [four equilibrium conditions (1) - (4)], the required four parameters are counted: 16 (L16), 17 (R17), 18 (L18), 19 (R19). The parameter values of elements 9 (R9), 11 (R11), 15 (R15) are constant and known. All adjustable balancing elements - 10 (L10), 14 (R14), 12 (L12), 13 (R13) 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, therefore their parasitic capacitances are absent relative to the ground.

Claims (1)

A bipolar parameter meter containing a supply pulse generator, which consists of pulse shapers with voltage changes over their duration according to the law K ₁ t ¹ , K ₂ t ² , K ₃ t ³ and K ₄ t ⁴ , where K ₁ , K ₂ , K ₃ and K ₄ 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, the output of which forms the first output of the pulse generator relate no "lands", sync block output is connected to the input (clock input) of each of the pulse, and its output forms a second output (output synchronization) pulse generator relative to "earth", 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 consists of two branches connected in parallel, the first of which includes a single resistor of the first shoulder of the bridge relationship and a two-terminal with elements of balancing the bridge circuit, the free output of a single resistor is connected to the first output of the pulse generator , the free output of a two-terminal with balancing elements is “grounded”, the common output of it and a single resistor forms the first output of the bridge circuit output, a two-terminal device with balancing elements consists of a first inductive coil and a circuit composed of a first resistor and a second inductive coil connected in series, a second resistor connected in parallel, the second branch of the bridge includes a single resistor of the second arm of the bridge relationship and two terminals for connecting two-terminal objects measurement, the free output of a single resistor is connected to the first output of the pulse generator, one of the terminals for connecting a two-pole of the measurement objects is “grounded”, the common terminal of the other terminal and the single resistor forms the second output terminal of the bridge circuit, the two-terminal network of the measurement object, in particular, consists of the first inductive coil and the circuit of the first resistor and second inductive coil connected in parallel to the common terminal of two inductive a second resistor is connected to the coils and this common terminal is connected to a grounded terminal for connecting two-terminal measuring objects; 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 resistor is introduced and the inclusion of bridge circuit elements is changed, an additional resistor is connected in parallel with the first inductive coil of the first branch of the bridge circuit, the common output of the first inductive coil, an additional resistor and the first resistor in the first branch of the bridge a is connected to the first output terminal of the bridge circuit, the common terminal of the first inductive coil and the first resistor in the second branch of the bridge circuit is connected to an ungrounded terminal for connecting two-terminal objects of measurement, the free terminal of the second resistor of the second branch of the bridge is connected to the common terminal of the first resistor available in this branch and second inductive coil.