SU913265A1 - Digital automatic extremal ac bridge for measuring one component of complex conductivity - Google Patents

Description

The invention relates to electrical engineering and can be used for high-speed high-speed measurement of one of the parameters of complex conductivity.

Known digital automatic extreme bridge for measuring one component of the complex conductivity O].

A disadvantage of this device is low speed.

Closest to the present invention is a digital automatic extremum AC bridge for measuring one component of complex conductivity, comprising a generator, a voltage transformer with a primary winding connected to the generator, and a secondary adjustable one and two unregulated windings to which the first exemplary measure is connected, respectively, one of the terminals object of measurement and serially connected controlled divider nap2

The second exemplary measure, the equilibrium detector, the alternating current converter is a direct voltage, the output of which is connected to the control input of the controlled voltage divider, and a current comparator with a pointing winding connected to the equilibrium detector, and two differential windings, one of which is connected from one side to the input of inverter tokpostoyannoe alternating voltage, and the other to the first and second exemplary clamp least the measurement object, and the second differential, the winding ¹⁵ is connected to W least the swarm model [2].

The disadvantage of the known bridge lies in the fact that its equilibrium detector contains a computing unit

20 m

performing a division operation.

The purpose of the invention is to simplify the digital automatic extremum bridge 'AC for measuring3 91

perception of one component of the complex conductivity.

This goal is achieved by the fact that in a digital automatic extremum AC bridge for measuring one component of complex conductivity, containing a generator, a voltage transformer with a primary winding connected to a generator, and secondary controlled and two unregulated windings to which the first model measure is connected, respectively from the terminals of the object of measurement and the series-connected controlled voltage divider and the second model measure, the equilibrium detector, The alternating current is a direct voltage, the output of which is connected to the control input of a controlled voltage divider, and a current comparator with a pointing winding connected to an equilibrium detector, and two differential windings, one of which is connected from one side to the converter input AC current - constant voltage, and, on the other hand, to the first exemplary measure and the second clamp of the measurement object, and the second differential winding is connected to the second Exemplary measure, the equilibrium detector of the bridge is designed as Consequently, the alternating current alternating current is a direct voltage, an analog-to-digital converter that accumulates the adder and is equipped with a comparator and two sources of reference voltage connected via a key to the reference input of the analog-digital converter, the output of the comparator is connected to the control input of the key, and the inputs are connected with the transducer outputs alternating current - constant voltage.

The drawing shows a block diagram of a digital automatic extremum AC bridge for measuring one component of the complex conductivity.

It contains the generator 1, the transformer 2 voltage from the primary. with a coil 3 connected to a generator, 'and secondary regulated 4 and unregulated windings 5 and 6, with the first exemplary measure 7 connected to the winding 4 and one of the winding 5

3265 4

clamps of an object 8 measurement, to the winding 6 - serially connected controlled voltage divider 9 and the second model measure 10, de ₅ equilibrium tector 11, alternating current converter 12 is a DC voltage, the output of which is connected to the control input of the voltage divider 9, comparator 13 currents with , 0 is a positive winding 14 connected to an equilibrium detector and two differential windings 15 and 16, with the winding 15 being connected on one side to the input of the converter 12,

, 5 and on the other hand, to the exemplary measure 7 and the second terminal of the measurement object 8, and the second differential winding 16 is connected to the second exemplary measure 10.

20 Simplification of this device is achieved due to the fact that the equilibrium detector 11 does not contain a computing unit used in a known bridge, but is made in the form of successively connected second transducer 17 alternating current — a constant voltage, analog-to-digital converter 18, accumulating adder 19 and equipped block 20

30 comparison and two sources 21 and 22 of the reference voltage, connected via a switch 23 to the reference input of the analog-to-digital converter, the output of the comparator unit 20 is connected

₃₅ to the control input of the key 23, and the inputs are connected to the outputs of the transducers 12 and 17.

High speed AC bridge ceteris paribus condition ditions ₄₀ provided through the use of a modified trim extrapolation method used in the known device. This method consists in that the damping effect is chosen proportional to the current value of the output signal of the bridge according to an adjustable parameter related to the modulation increment of this signal.

In a known bridge, a computing unit is used to generate such an impact, which complicates the device.

50

In the proposed bridge regulatory. the effect is chosen directly proportional to the ⁵⁵ current module 1 1 ^ | imbalance signal of the bridge circuit, and the proportionality coefficient can take two values that differ

5 9

<2 * ^ 1.41 times. As a selection criterion nuzhyogo value the proportionality factor is the ratio of currents modules I _ί,; | and | 1 ^ 1 bridge q (^ pi (see drawing), where C is the differential current of the first exemplary measure and object of measurement, and is the disequilibrium current of the bridge circuit.

The structure of the bridge circuit is such that the complex current is determined by the equality

Ϊ2 = * e (and) -1MC) +) and C) 1 + Ltod (1)

where Bp (C) and! t (* l) “are respectively the real and imaginary components of the complex current, so that

C = MG) + _ NPG (14) (2)

In order to simplify the calculations in equality (1), it is assumed that the product of the transfer coefficients of the converter 12 and the controlled divider 9 is equal to one.

If the current components satisfy the equality

1t (M) = νΓ · МЬ), (3),

12.1 are equal

then the modules of the currents between themselves.

Equalities (1) and (2) imply that for '1о> () <"hGZK & () the inequality holds

Shch1>

(four)

In this case, the dependence of the current modulus ί m on the degree of disequilibrium 1gp (C) in a discretely adjustable parameter is fairly accurately approximated by a linear function with a proportionality coefficient equal to unity.

If 1t (q)> ttne! C), then the modules of the currents / and. ^. satisfy inequality

| 1D (<H _g 1. (5)

In this case, the dependence of the current modulus) on the degree of disequilibrium with respect to the discrete-adjustable parameter can also be approximated by a linear function, but with a proportionality coefficient equal to π 1, 41

Thus, the fact that one of the relations (4) or (5) is fulfilled may serve as a basis for choosing the proportionality coefficient K between the current modulus | ΐ ^ | a bridge circuit and an extrapolation estimate of its disequilibrium, or equal to this estimate by the regulatory effect p on a discretely adjustable parameter

p = k ( ₂

(6)

13265

where

15

20

25

thirty

K if And / <| 1 ₂ | . (7)

* This is the essence of balancing this bridge.

It follows from calculations that the accuracy for regulating cart ₁₀ action in accordance with formulas (6) and (7) as proposed bridge does not exceed an average of that of the known bridge.

Therefore, with equal measurement accuracy in both devices, it is necessary on average to have the same number of balancing cycles in order to achieve an equilibrium state. This means that the speed of the known and proposed bridges is the same. At the same time, the absence of a computing device in a real bridge leads to the fact that it is substantially simpler than a known bridge.

The bridge works as follows.

In the initial state, the content of accumulating adder 19 is zero. The number of turns of the adjustable winding 4 of the transformer 2 is also zero and the current through the model measure 7 does not flow. At the beginning of the bridge balancing cycle, using block 20, a comparison of voltages proportional to current modules ₃₅ > Ig-1 · θ is performed, depending on the comparison result, using a switch 23, one of sources 21 or 22 is connected to the reference input of analog-digital converter 18 to ₄₀ toth differ in λί? 1.41 times This ensures the selection of the required value of the transfer coefficient of the analog-to-digital converter and, ultimately, the proportionality coefficient between the regulating influence and the 11-c-1 module in accordance with formulas (6), (7). Quantitatively regulating effect can be estimated by the numerical value of the output code of the converter 18. This code is fed into the cumulative adder 19 and stored there. Simultaneously produced changing the number of turns of the winding 4 in an amount proportional to the increment contents of adder ⁵⁵ scheniyu · 19. Thereby, discrete balancing of the bridge is carried out according to the measured component of the complex conductance. It also balances on the second, unmeasurable component by changing the transmission coefficient of the controlled voltage divider 9 / by changing its control signal (output voltage of the converter 12).

In the subsequent cycles, the described balancing algorithm repeats' until a balance is reached with a given accuracy. At the same time, the output signal of the measuring circuit is reduced to such an extent that the result of its analysis with the aid of an analog-digital converter is less than a discrete unit, as a result of which the number recorded in the adder does not change. The contents of the adder 19 in this case is the result of measurement. 20

Thus, this bridge, in comparison with the known device, is distinguished by greater simplicity of implementation with equality of the basic technical characteristics (for example, speed, accuracy, accuracy) due to the absence of a computing unit.

Claims (1)

Claim thirty Digital automatic extremum AC bridge for measuring one component of complex conductivity, containing a generator- ₃₅ torus, a voltage transformer with a primary winding connected to a generator, and secondary regulated and two unregulated windings to which 40 are connected, respectively, the first exemplary measure, one of them presses of the measurement object and a series-connected controlled voltage divider and a second model measure, an equilibrium detector, an alternating current converter — a direct voltage, the output of which is connected to the control input of the controlled a voltage divider, and a current comparator with a pointer winding connected to an equilibrium detector, and two differential windings, one of which is connected from one side to the input of the converter. An alternating current is a constant voltage, and on the other to the first exemplary measure and the second terminal of the measurement object, and the second differential winding is connected to the second exemplary measure, which differs from me in that, in order to simplify the device, the bridge equilibrium detector is made in the form of a second converter connected in series alternating current - DC voltage, analog-to-digital converter, accumulating adder and equipped with a comparator and two sources of reference voltage, connected via a key to the reference input of the analog-digital converter, the output of the comparator is connected to the control input of the switch, and the inputs are connected to the outputs of the converters alternating current - constant voltage.