RU2525717C1 - Bridge meter of bipoles parameters - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: bridge meter of bipoles parameters comprises a generator of feed pulses, comprising a synchronisation cascade, shapers of linearly varying, square-law and cubic pulses, a switchboard and a power amplifier, a four-arm bridge circuit, which comprises two parallel connected branches, the first of which comprises two serially connected resistors, and the second branch comprises serially connected first resistor, the second resistor and inductance coil. At the same time the second branch of the four-arm bridge circuit includes two terminals for connection of bipoles of the measurement object, one of terminals is grounded, the bipole of the measurement object, in particular, comprises the serially connected first capacitor and resistor, in parallel to which the second capacitor is connected, two outputs of the outlet of the four-arm bridge circuit are connected to a differential inlet of the zero-indicator, its other inlet - synchronisation inlet is connected to the second outlet of the generator of feed pulses, the common bus of the zero indicator is grounded. Besides, the device includes an additional inductance coil and an additional resistor.

EFFECT: lower error of measurement due to exclusion of an error component from parasitic capacitance relative to earth of a non-earthed multi-element bipole, and also instability of this parasitic capacitance due to usage of only earthed multi-element bipoles.

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Description

The invention relates to industrial electronics, automation, information-measuring equipment and can be used to control and determine the parameters of two-terminal devices.

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., 1985, No. 19], containing a series-connected pulse generator with voltage change over their duration according to the law of power functions, a four-arm bridge circuit and a zero indicator.

Its disadvantage is the inability to ground both existing multi-element bipolar. All other 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 not stable and, as is known, varies significantly over time and especially with temperature. In the particular case, with 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 non-grounded. 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 Maxwell bridges [Nizhny S.M. AC bridges. - M.-L.: Energy, 1966, - 88 p., P. 40, fig. 15], Heya [Nizhny S.M. AC bridges. - M.-L.: Energy, 1966, - 88 p., P. 40, fig. 16], Anderson [Nizhny S.M. AC bridges. - M.-L.: Energy, 1966, - 88 p., P. 42, Fig. 18].

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., 1981, No. 3]. The bridge meter contains a trapezoidal pulse generator, a four-arm bridge circuit, and a zero indicator connected in series.

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 with respect to the “ground” of the non-earthed multi-element bipolar, as well as the instability of this parasitic capacitance, through the use of only earthed multi-element bipolar.

This is achieved by the fact that in a bridge two-terminal parameter meter containing a supply pulse generator, consisting of a synchronization cascade, rammers, quadratic and cubic 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 are 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 power pulse generator relative It is 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 input of the four-arm bridge circuit, which consists of two branches connected in parallel, the first of which 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 resistor is grounded, the common output of these two x resistors forms the first output terminal of the four-arm bridge circuit, the second branch of the four-arm bridge circuit consists of series-connected first resistor, second resistor and inductor, the third resistor is connected to the common terminal of the second resistor and inductor, the common terminal of the first and second resistors forms the second output terminal the bridge circuit, also the second branch of the four-arm bridge circuit includes two terminals for connecting the two-pole object of the measurement, one of the terminals is grounded, two-pole to the measurement object, in particular, consists of a series-connected first capacitor and a resistor, in parallel with which a second capacitor is connected, two outputs of the four-arm bridge circuit output are connected to the differential input of the zero indicator, its other input, the synchronization input, is connected to the second output of the supply pulse generator, the common bus of the zero indicator is grounded, an additional inductor is introduced, an additional resistor and the inclusion of elements is changed, an additional inductor is turned on between the free terminal of the third resistor of the second bridge branch chetyrehplechey circuit and the "ground", and a further resistor connected between the second output terminal of the bridge circuit and unused terminal for connecting two-terminal measuring object.

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

The bridge measuring instrument of the two-terminal parameters contains a supply pulse generator 1, consisting of a shaper 2 of linearly changing pulses (K ₁ t ¹ ), a shaper of 3 quadratic pulses (K ₂ t ² ), a shaper of 4 cubic pulses (K ₃ t ³ ), where K ₁ K ₂ and K ₃ are constant coefficients, t is the current time of the 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 linearly varying, quadratic and cubic 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 generator 1 of the supply pulses relative to the "ground". The second output of the generator 1 of the supply pulses relative to the "ground" - 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 supply pulse generator 1 is connected to the input (with the first peak of the generator diagonal) of the four-arm bridge circuit, 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 series-connected first resistor 10 (R10), a second resistor 11 (R11) and an inductor 12 (L12). The common output of resistors R8 and R10 forms the first peak of the generator diagonal of the four-arm bridge circuit. The common terminal of resistors R10 and R11 forms the second terminal of the output (second peak of the measuring diagonal) of the four-arm bridge circuit. The free terminal of the inductor L12 is grounded. A third resistor 13 (R13) is connected to the common terminal of the resistor R11 and the inductor L12, and an additional inductor 14 (L14) is connected in series with it, the free terminal of which is grounded. An additional resistor 15 (R15) is connected to the common output of resistors R10 and R11, the resistance value of which is equal to the resistance value of resistor R11. To the free terminal of the resistor R15 is connected one of the two terminals for connecting the two-terminal device of the measurement object. The other terminal is grounded. The bipolar of the measurement object, in particular, consists of a series-connected first capacitor 16 (C16) and a resistor 17 (R17), in parallel with which a second capacitor 18 (C18) is connected. Two outputs of the four-arm bridge circuit output are connected to the differential input of the zero indicator 19. Another input of the zero indicator 19 is the synchronization input connected to the second output of the supply pulse generator 1. The common bus of the zero indicator 19 is connected to the common output of the resistor R9 and inductors L12 and L14, forming 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, R10, R11 and R15 are known and constant. The parameters are the parameters of the capacitors C16 and C18 and the resistor R17, forming a two-terminal device of the measurement object. Adjustable balancing variables are known parameters of resistor R13 and inductors L12 and L14.

The work of a bridge measuring device of two-terminal parameters is as follows. At the initial instant of time, the voltages on the generator and measuring diagonals of the four-arm bridge circuit are zero. Mathematical expressions of the equilibrium conditions of the four-arm bridge chain will have a simpler form when the equalities

$$R_8=R_{10},\left(\mathrm{one}\right)$$

$$R_9=R_{\mathrm{eleven}}=R_{\mathrm{fifteen}}.\left(2\right)$$

Therefore, below the equilibrium conditions of the four-arm bridge chain are given taking into account the preliminary fulfillment of these equalities.

In the generator 1 of the supply pulses, the shaper 2 of linearly varying pulses, the shaper 3 of quadratic pulses, the shaper 4 of cubic pulses form a sequence of pulse signals of the corresponding shape. Through the switch 6 and the power amplifier 5, these signals are alternately fed to the output of the supply pulse generator 1 and then act on the generator diagonal of the four-arm bridge circuit.

First of all, a sequence of pulse signals of linearly varying voltage is fed to the input of the four-arm bridge circuit. When the next such pulse is applied, in the measuring diagonal of the four-arm bridge circuit after the end of the transient, a non-equilibrium voltage is established that does not change during the time interval from the end of the transient to the end of the pulse. The flat peak of this voltage is reduced to zero by a single adjustment of the variable balancing element L12. As a result, the first equilibrium condition of the four-arm bridge chain, which has the form

$$L_{12}-R^2{}_{\mathrm{eleven}}{C}_{16}=0.\left(3\right)$$

Then, a sequence of quadratic pulses arrives at the generator diagonal of the four-arm bridge circuit. Under the influence of the next quadratic-shaped pulse at the output of the four-arm bridge circuit after the end of the transition process, a pulse signal of non-equilibrium with a flat top is established during the time interval from the end of the transition process to the end of the pulse. This vertex, taking into account the fulfilled first equilibrium condition (3), is reduced to zero by a single adjustment of the variable balancing element R13. The second equilibrium condition for the four-arm bridge chain is written as

$$R_{13}=R_{17}-R^2{}_{\mathrm{eleven}}\left(\mathrm{four}\right)$$

The fulfillment of the first equilibrium condition (3) in this case is preserved, since this condition does not contain a variable adjustable balancing element R13.

Lastly, cubic-shaped pulses act on the generator diagonal of the four-arm bridge circuit. In the measuring diagonal of the four-arm bridge circuit under the influence of the next pulse of a cubic shape, a pulse signal of disequilibrium is established. This signal after the end of the transient during the time interval from the end of the transient to the end of the pulse has a flat top, which under conditions (3) and (4) is reduced to zero by a single adjustment of the variable balancing element L ₁₄ . In this case, the third equilibrium condition of the four-arm bridge chain is determined by the expression

$$L_{\mathrm{fourteen}}-R^2{}_{\mathrm{eleven}}{C}_{\mathrm{eighteen}}=0.\left(5\right)$$

The previous equilibrium conditions (3) and (4) are preserved, since under these conditions there is no variable adjustable balancing element L ₁₄ .

The required values of the parameters of the three elements of the two-terminal network of the measurement object C16, R17 and C18 are determined from the three equilibrium conditions of the four-arm bridge circuit (3) - (5). Thus, three unknown parameters are found from the solution of essentially three equations.

Consequently, the proposed bridge meter of the two-terminal parameters 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, as well as the instability of this parasitic capacitance, due to the use of only earthed multi-element two-terminal devices. Also, in the proposed bridge meter of two-terminal parameters, separate balancing and separate counting are implemented.

Claims (1)

A bridge two-terminal parameter meter containing a power pulse generator, consisting of a synchronization cascade, rammers, ramps and cubic 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 are connected to the inputs of the switch, the output of which connected to the input of the power amplifier, the output of the power amplifier forms the first output of the power pulse generator relative to the "ground", the second output d of the supply pulse generator - the synchronization output forms the output of the synchronization cascade, the common bus of the supply pulse generator is earthed, the first output of the supply 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 consists of two resistors connected in series, free the output of one of them is connected to the first output of the supply pulse generator, and the free output of the other resistor is grounded, the common output of these two resistors forms the output terminal of the four-arm bridge circuit, the second branch of the four-arm bridge circuit consists of a series resistor, a second resistor and an inductor, a third resistor is connected to the common terminal of the second resistor and an inductor, the common terminal of the first and second resistors forms the second output terminal of the bridge circuit, Also, the second branch of the four-arm bridge circuit includes two terminals for connecting the two-terminal devices of the measurement object, one of the terminals is grounded, the two-terminal device of the measurement, per hour In fact, it consists of a first capacitor and a resistor connected in series, a second capacitor is connected in parallel, two outputs of the four-arm bridge circuit output are connected to the differential 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 grounded, characterized in that an additional inductor is inserted into it, an additional resistor and the inclusion of elements is changed, an additional inductor is included for between the free terminal of the third resistor of the second bridge branch chetyrehplechey circuit and the "ground", and a further resistor connected between the second output terminal of the bridge circuit and unused terminal for connecting two-terminal measuring object.