RU2569043C2 - Bridge meter of two-terminal circuit parameters - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: invention relates to industrial electronics, automatics, INFO technologies and can be used for control and determination of two-terminal circuit parameters. Claimed device comprises series-connected supply pulse generator, hybrid circuit and zero-indicator. Additionally, it incorporates three resistors, inductor while two terminals for connection of measurement subject are transferred from the bridge first arm to second one.

EFFECT: decreased errors owing to ruled out errors of parasitic capacitance relative to ground of unearthed multi-element two-terminal circuit.

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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, as well as physical quantities by means of parametric sensors included in the electric bridge.

 Known bridge meter parameters of multi-element passive two-terminal [ed. St. USSR No. 1157467, G01R 17/10. Bridge meter of parameters of multi-element passive two-terminal / G.I. Peredelsky. - Publ. in bul., 1985, No. 19], containing a series-connected supply pulse generator with voltage changes over their duration according to the law of power functions, a bridge electrical 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. The non-earthed multi-element bipolar forms a parasitic capacitance relative to the “earth”, 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 of an ungrounded bipolar with adjustable balancing elements and using matrices of the same type as elements, controlled keys and control 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 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 s, p. 42, Fig. 18].

 Known electric bridge [ed. St. USSR No. 920532, G01R 17/10. Electric bridge / G.I. Peredelsky. - Publ. in bull., 1982, No. 14.], containing a serially connected feed generator of trapezoidal pulses, a bridge electrical circuit and a zero indicator.

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

 The closest in technical essence and the achieved result to the claimed device is selected as a prototype bridge meter parameters four-element passive two-terminal [ed. St. USSR No. 918862, G01R 17/10. Bridge meter of parameters of four-element passive two-terminal / G.I. Peredelsky. - Publ. in bull, 1982, No. 13], containing a serially connected feed generator of trapezoidal pulses, a 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 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 meter of two-terminal parameters, it contains a supply pulse generator, consisting of pulse shapers with voltage changes over their duration according to the law K ₁ t, K ₂ t ² , K ₃ t ³ , K ₄ t ⁴ , K ₅ t ⁵ , where K ₁ , K ₂ , K ₃ , K ₄ , K ₅ are constant coefficients and t is the current time from the switch, from the power amplifier and the synchronization cascade, the output of the synchronization cascade is connected to each input of the available five pulse shapers, the outputs which are connected to the inputs of the switch, the output of which is connected to Odom power amplifier, the power amplifier output forms the first output of the generator supplying pulses relative to "earth", the second output of the generator supplying pulses - synchronization output constitutes the output stage of synchronization, the overall tire generator feeding pulses grounded; the first output of the supply pulse generator is connected to the input of the four-arm bridge circuit (bridge), which forms the common output of two parallel branches of the four-arm bridge circuit, the first of these two branches consists of two series-connected resistors, the free output of the first of them is connected to the first output of the supply generator pulses, the common output of these two resistors forms the first output terminal of the four-arm bridge circuit, the free output of the second resistor is grounded, the second branch of the bridge consists of the first and second resistors and the inductor are connected separately, there is also a series-connected capacitor and a third resistor, the free output of the capacitor is connected to the common output of the second resistor and the inductor, the free output of the first resistor of the second bridge branch is connected to the first output of the supply pulse generator, the common output the first and second resistors of the second branch of the bridge forms the second output terminal of the four-arm bridge circuit, the free terminal of the inductor is grounded, also four the bridging bridge circuit includes a measurement object, which, in particular, consists of a series-connected first capacitor, a first resistor and an inductor, and a second resistor and a second capacitor are connected in parallel with the latter; a null indicator, the two terminals of the differential (first) input of which are connected to the two terminals of the output of the four-arm bridge circuit, the second input (synchronization input) of the null indicator is connected to the second output of the supply pulse generator, the common bus of the null indicator is grounded; three additional resistors, an additional inductor, and two terminals for connecting the measurement object are transferred from the first branch to the second branch of the bridge, the first additional resistor is connected in parallel with the existing inductor of the second branch of the four-arm bridge circuit, an additional inductor is connected between the free terminal of the existing third resistor in the second branch and “ground”, parallel to the second resistor in the second branch of the four-arm bridge branch, the last the second and third additional resistors are connected properly, the first terminal for connecting the two-terminal terminal of the measurement object is connected to the common terminal of the latter, the second terminal is grounded, the free terminal of the first capacitor of the measurement object is connected to the first terminal, and the common terminal of the inductor, second resistor and second capacitor of the measurement object with a second terminal for connecting the two-terminal terminal of the measurement object.

 The invention is illustrated in the drawing.

The bridge measuring device of two-terminal parameters contains a generator 1 of supply pulses, 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 ), a shaper of 5 pulses, the voltage of which varies according to the law of the fourth degree (K ₄ t ⁴ ), the shaper of 6 pulses, the voltage of which changes according to the law of the fifth degree (K ₅ t ⁵ ), where K ₁ , K ₂ , K ₃ , K ₄ , K ₅ are constant coefficients , t - current time, power amplifier 7, switch 8 and stage 9 synchron tion. The output of each pulse shaper is connected to the corresponding input of the switch 8, the output of which is connected to the input of the power amplifier 7, the output of which forms the first (signal) output relative to the "ground" of the generator 1 of the supply pulses. The output of the synchronization stage 9 is connected to the input (synchronization input) of each pulse shaper. Also, the output of the synchronization cascade 9 forms a second output (synchronization output) relative to the ground of the supply pulse generator 1. The common bus of the generator 1 of the supply pulses is grounded.

 The first output of the generator 1 of the supply pulses is connected to the input (to the first vertex of the generator diagonal) of the four-arm bridge circuit (bridge), formed by two parallel connected branches. The first of these branches consists of two series-connected resistors 10 (R10) and 11 (R11), forming the first and second shoulders of the four-arm bridge circuit, respectively. The free output of the first resistor R10 is connected to the first output of the supply pulse generator 1. The free terminal of the second resistor R11 is grounded. The common output of resistors R10 and R11 forms the first output terminal (the first peak of the measuring diagonal) of the four-arm bridge circuit.

 The second branch of the bridge consists of a series-connected first resistor 12 (R12), a second resistor 13 (R13) and an inductor 14 (L14). The first resistor R12 forms the third arm of the bridge. With its free output, this resistor is connected to the first output of the supply pulse generator 1. The common terminal of resistors R12 and R13 forms the second output terminal (second vertex of the measuring diagonal) of the bridge. The second resistor R13 and the inductor L14 are part of a multi-element bipolar circuit that forms the fourth arm of the four-arm bridge circuit. In this bipolar, parallel to the inductor L14, a first additional resistor 15 (R15) and a series capacitor 16 (C16), a third resistor 17 (R17) and an additional inductor 18 (L18) are connected. Also in this two-terminal network, in parallel with the resistor R13, a second additional resistor 19 (R19) and a third additional resistor 20 (R20) connected in series are connected, to the common terminal of which a first terminal for connecting the two-terminal device of the measurement object is connected. The free terminal of resistor R19 is connected to the common terminal of resistor R13 and inductor L14. The free terminal of resistor R20 is connected to the common terminal of resistors R12 and R13 and to the second vertex of the measuring diagonal of the four-arm bridge circuit. The second terminal for connecting the bipolar of the measurement object is grounded.

 The bipolar of the measurement object, in particular, consists of a series-connected first capacitor 21 (C21), a first resistor 22 (R22) and an inductor 23 (L23), in parallel with which a second resistor 24 (R24) and a second capacitor 25 (C25) are connected. The free terminal of the first capacitor C21 is connected to the first terminal for connecting the two-terminal device of the measurement object. The common output of the inductor L23, the second resistor R24 and the second capacitor C25 is connected to the second terminal for connecting the two-terminal device of the measurement.

 Two outputs of the differential first input of the null indicator 26 are connected to two outputs of the output of the four-arm bridge circuit. The second input (synchronization input) of the null indicator 26 is connected to the second output of the supply pulse generator 1. The common bus of the null indicator 26 is connected to the grounded common bus of the generator 1 of the supply pulses and to the second vertex of the generator diagonal of the bridge formed by the common output of resistors R11 and R15, inductors L14 and L18 and the second terminal for connecting the two-terminal object of measurement.

 In a bridge meter of two-terminal parameters, the resistance values of resistors R10 and R12, R13 and R20 are constant, known and equal (R10 = R12, R13 = R20). The constant value of the resistance of the resistor R19 is also known. The resistance value of the resistor R11 is determined from the pre-fulfilled initial condition

(1) $$R_{{}_{{}_{\mathrm{eleven}}}}=\frac{R_{{}_{13}}(R_{{}_{13}}+R_{{}_{19}})}{2R_{{}_{13}}+R_{{}_{19}}}.$$

(one)

Adjustable variables are known parameters of balancing elements - inductors L14 and L18 and resistors R15 and R17 and capacitor C16. Searched are the parameters of the bipolar elements of the measurement object - capacitors C21 and C25, resistors R22 and R24 and inductors L23.

 The work of a bridge measuring device of two-terminal parameters is as follows. At the initial time, in the absence of pulses from the generator 1, the supply voltage pulses on the generator and measuring diagonals of the four-arm bridge circuit are equal to zero. In the generator 1 of supply pulses, the shaper 2 of linearly varying pulses, the shaper 3 of quadratic pulses, the shaper 4 of cubic pulses, the shaper 5 pulses, the voltage of which varies according to the law of the fourth degree, the shaper 6 pulses, the voltage of which changes according to the law of the fifth degree, form a sequence of pulse signals corresponding forms. Through the switch 8 and the power amplifier 7, these signals are alternately fed to the output of the supply pulse generator 1 and act on the generator diagonal of the four-arm bridge circuit.

 First of all, a sequence of linearly changing pulse signals 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 inductance of the balancing inductor L14. In this case, the first equilibrium condition of the four-arm bridge chain is satisfied

And ₁ = (2R ₁₃ + R ₁₉ ) ² L ₁₄ - R ² ₁₃ R ² ₁₉ C ₂₁ = 0. (2)

 Secondly, a sequence of quadratic pulses arrives at the generator diagonal of the four-arm bridge circuit. Under the action of the next quadratic-shaped pulse at the output of the four-arm bridge circuit after the end of the transition process, an impulse non-equilibrium signal with a flat top is generated during the time interval from the end of the transition process to the end of the pulse. This peak, taking into account the fulfilled first (2) equilibrium condition, is brought to zero by a single adjustment of the variable resistance of the balancing element - resistor R15. The second equilibrium condition for the four-arm bridge chain is written as

A ₃ = (2R ₁₃ + R ₁₉ ) ² R ₁₅ R ₂₂ - R ² ₁₃ R ² ₁₉ = 0. (3)

The fulfillment of the first equilibrium condition (2) in this case is preserved, since it does not have a variable resistance of the balancing resistor R15.

 Then, a sequence of cubic pulses arrives at the generator diagonal of the four-arm bridge circuit. When the next impulse of a cubic form is exposed to the output of the four-arm bridge circuit after the end of the transition process, a pulse equilibrium signal with a flat top is established during the time interval from the end of the transition process to the end of the pulse. This peak, taking into account the fulfilled first (2) and second (3) equilibrium conditions, is brought to zero by a single adjustment of the variable capacitance of the balancing capacitor C16. The third equilibrium condition of the four-arm bridge chain is written as

A ₃ = (2R ₁₃ + R ₁₉ ) ² L ₂₃ - R ² ₁₃ R ² ₁₉ C ₁₆ = 0. (four)

The fulfillment of the first (2) and second (3) equilibrium conditions in this case is preserved, since they do not contain a variable capacitance of the balancing capacitor C16.

 Further, pulses whose voltage varies according to the law of the fourth degree act on the generator diagonal of the four-arm bridge circuit. When the next such pulse arrives in the measuring diagonal of the bridge, a nonequilibrium signal appears. This pulse signal after the end of the transient during the time interval from the end of the transient to the end of the pulse contains a flat peak, which under the conditions (2) - (4) is reduced to zero by a single adjustment of the variable resistance of the balancing resistor R17. The fourth equilibrium condition of the four-arm bridge chain is determined by the expression

A ₄ = (2R ₁₃ + R ₁₉ ) ² R ₁₇ R ₂₄ - R ² ₁₃ R ² ₁₉ = 0. (5)

The previous equilibrium conditions (2) - (4) are preserved, since under these conditions there is no variable resistance of the balancing resistor R17.

 Lastly, a sequence of pulses is fed to the input of the bridge, the voltage of which varies according to the law of the fifth degree. The impact on the bridge circuit of the next pulse of this shape causes the appearance of a pulse disequilibrium signal in the measuring diagonal of the bridge, which has a flat top after the end of the transient during the time interval from the end of the transient to the end of the pulse. This vertex is reduced to zero under conditions (2) - (5) by a single adjustment of the variable inductance of the balancing inductor L18. As a result, the fifth and final equilibrium condition of the four-arm bridge chain, which has the form

A ₅ = (2R ₁₃ + R ₁₉ ) ² L ₁₈ - R ² ₁₃ R ² ₁₉ C ₂₅ = 0. (6)

In this case, the equilibrium conditions (2) - (5) are not violated, since they do not have a variable inductance of a balancing inductor L18.

 The desired parameter values of the five elements of the two-terminal device of measurement C21, R22, L23, R24 and C25 are determined from the five equilibrium conditions of the four-arm bridge chain (2) - (6). In fact, five unknown parameters are determined from the solution of five equations.

 Thus, 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 grounded multi-element two-terminal devices. In addition, the proposed bridge meter of the two-terminal parameters implements such an important property of bridge circuits as dependent separate balancing.

Claims (1)

A bipolar bridge parameter meter containing a supply pulse generator, consisting of pulse shapers with voltage changes over their duration according to the law K ₁ t, K ₂ t ² , K ₃ t ³ , K ₄ t ⁴ , K ₅ t ⁵ , where K ₁ , K ₂ , K ₃ , K ₄ , K ₅ - constant coefficients and t - current time, from the switch, from the power amplifier and the synchronization cascade, the output of the synchronization cascade is connected to each input of the available five 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, Exit forms a first power amplifier feeding the pulse generator output relative to "earth", the second output of the pulse generator feeding - synchronization output constitutes the output stage of synchronization, the overall tire generator feeding pulses grounded; the first output of the supply pulse generator is connected to the input of the four-arm bridge circuit (bridge), which forms the common output of two parallel branches of the four-arm bridge circuit, the first of these two branches consists of two series-connected resistors, the free output of the first of them is connected to the first output of the supply generator pulses, the common output of these two resistors forms the first output terminal of the four-arm bridge circuit, the free output of the second resistor is grounded, the second branch of the bridge consists of the first and second resistors and the inductor are connected separately, there is also a series-connected capacitor and a third resistor, the free output of the capacitor is connected to the common output of the second resistor and the inductor, the free output of the first resistor of the second bridge branch is connected to the first output of the supply pulse generator, the common output the first and second resistors of the second branch of the bridge forms the second output terminal of the four-arm bridge circuit, the free terminal of the inductor is grounded, also four the bridging bridge circuit includes a measurement object, which, in particular, consists of a series-connected first capacitor, a first resistor and an inductor, and a second resistor and a second capacitor are connected in parallel with the latter; a null indicator, the two terminals of the differential (first) input of which are connected to the two terminals of the output of the four-arm bridge circuit, the second input (synchronization input) of the null indicator is connected to the second output of the supply pulse generator, the common bus of the null indicator is grounded; characterized in that three additional resistors, an additional inductor, and two terminals for connecting the measurement object are transferred from the first branch to the second branch of the bridge, the first additional resistor is connected in parallel with the existing inductor of the second branch of the four-arm bridge circuit, the additional inductor is included between the free terminal of the existing third resistor in the second branch and the “ground” parallel to the second resistor in the second branch of the four-arm mos In the main branch, the second and third additional resistors are connected in series, the first terminal for connecting the two-terminal terminal of the measurement object is connected to the common terminal of the latter, the second terminal is grounded, the free terminal of the first capacitor of the measurement object is connected to the first terminal, and the common terminal of the inductor, second resistor, and second capacitor the measurement object is connected to the second terminal for connecting the two-terminal device of the measurement.