SU1455324A1 - A.c. transformer bridge for measuring impedance parameters - Google Patents

Abstract

The invention relates to electrical measuring technology and can be used in devices for determining the impedance parameters of mainly small values. The purpose of the invention — extending the measurement range towards low impedances and improving the measurement accuracy of these quantities — is achieved by functional adjustment of the elements of the measuring circuit. To do this, a second transformer 6, for example, with windings 7 and 8 and five switches 22-26, is additionally introduced into the AC transformer bridge, with the help of which a functional reorganization of the measuring circuit and configuration is carried out, and balancing occurs in the current-voltage comparison circuit. zheniy. 1 il. with p (L S

Description

at

21 current terminals for connecting the measurement object, the second terminals of the first Bf-ix of the main windings 4 and 10 of the first voltage transformer 2 and the comparator 9 currents are connected together. The first output of the secondary winding 8 of the second voltage transformer 6 is connected to the connection point WTO 1455324

I The invention relates to electrical measuring equipment and can be used in the construction of measuring instruments designed to determine the parameters of complex resistances of predominantly small values.

The purpose of the invention is to expand the range of measurements in the direction of small, immobile fixed contact 36 primary chances and increase the accuracy of the measuring switch 22 and the first non-connection of these quantities due to the functional contact 33 of the second switch- 1 of the first adjustment of the measuring element 23 with the first In the example of the main circuit, sample measure 15, the second output of the drawing is represented by the structure connected to the movable contact of the transformer bridge 29 of the third switch 24, and the ijiepeMeHHoro current. I Transformer bridge contains a power source 1, the first transformer top 2 voltage from the primary 3, the OS-20 voltage follower 14 is connected to the first secondary 4 and auxiliary to the movable contact 28 of the second switch 22, and the output to the first output of the additional standard measure 16 The second terminal of which is connected to the movable contact 30 of the fourth switch 25, and its fixed contacts 35 and 39 are connected to the terminals of the auxiliary winding 12 of the comparator 9 currents. The first output of the output: the winding 13 of the comparator 9 these fixed contacts 34 and 38 are connected to the terminals of the second main winding 11 of the comparators 9 currents. entrance

ptorichnoy 5 windings, the second trans-supercharger 6 voltage from the primary 7 and secondary 8 windings, the comparator 9 currents from the first 10 and second 11-25 {equal, auxiliary 12 and output 13 windings, the follower 14 voltage, the main 15 and additional 16 exemplary measures, T7 object, Zbreny, primary 18 and auxiliary 30

1 | 19th potential and primary 20 and

auxiliary 21 current terminals for r | connection of the object 17 measurements, r | first 22, second 23, third 24, four | 25 and fifth 26 switches with 1 sliding 27-31, first fixed, to | and 32- 35 and second fixed 36 contacts, respectively; an additional resistor 41, an equilibrium detector 42, resistors 43-46, symbol- ,. stray parasitic resistances of the potential and current portions of the branch of the Object 17 measurements.

The primary winding 3 of the transformer 2 voltage through the mobile 27 and | The first fixed 32 pins of the first-E 22 nd switch together with the voltage winding 7 of the second trans- voltage | 6 and the second non-moving contact 37 of the second transducer | Latch 23 are connected to the power supply 1. The first voltages of the main 4 and auxiliary 5 secondary windings of the first transformer 2 of the voltage are connected to the main 18 and auxiliary 19 potential, and the first outputs of the first main 10 and auxiliary 12 comparator windings 9

50

The coke is connected to the movable contact 31 of the fifth switch 26 and the first terminal of the additional resistor 41 whose second terminal, together with the fixed contact 40 of the fifth switch 26, is connected to the input of the detector 42. equilibrate. The second terminals of the primary windings 3 and 7 of the first 2 and secondary windings 5 and 8 of the second 6 voltage transformers, respectively, as well as the windings 11 and 13 of the comparators 9 currents, together with the second fixed contact 38 of the third switch 24 and the common wires x of the power source 1 and the equilibrium detector 43 are connected to bschey bus bridge.

The device works as follows.

After connecting to the terminals 18-21 of the object bridge 17, the measurement range is selected, during which the corresponding configuration of the measuring circuit is established by means of the circuit collector switches 22-26. Moreover, if the impedance of the object 17 of the measurements Zj npeBbraaeT total parasitic coKtOB is to the main 20 and an auxiliary 21 current terminals for connecting the object of measurement, the second terminals of the first Bf-ix main windings 4 and 10 of the first voltage transformer 2 and the comparator 9 currents are connected by myself. The first terminal of the secondary winding 8 of the second transformer 6 voltage is connected to the connection point in the second connected to the movable contact 29 of the third switch 24, and

The voltage follower 14 is connected to the movable contact 28 of the second switch 22, and the output to the first pin of an additional exemplary measure 16, the second pin of which is connected to the movable pin 30 of the fourth switch 25, and its fixed contacts 35 and 39 are connected to the bottom windings 12 comparator 9 currents. The first output of the output: the winding 13 of the comparator 9 these fixed contacts 34 and 38 are connected to the terminals of the second main winding 11 of the comparators 9 currents. entrance

 ,

five

0

The coke is connected to the movable contact 31 of the fifth switch 26 and the first terminal of the additional resistor 41 whose second terminal, together with the fixed contact 40 of the fifth switch 26, is connected to the input of the detector 42. equilibrate. The second terminals of the primary windings 3 and 7 of the first 2 and secondary windings 5 and 8 of the second 6 voltage transformers, respectively, as well as the windings 11 and 13 of the comparators 9 currents, together with the second fixed contact 38 of the third switch 24 and the common wires x of the power source 1 and the equilibrium detector 43 are connected to bschey bus bridge.

The device works as follows.

After connecting to the terminals 18-21 of the object bridge 17, the measurement range is selected, during which the corresponding configuration of the measuring circuit is established by means of the circuit collector switches 22-26. Moreover, if the impedance of the object 17 measurements Zj npeBbraaeT total parasitic resistance Z

Lor

branches of the measurement object, then the bridge establishes such a configuration of the measuring circuit, in which its equilibration is carried out according to a scheme for comparing currents or more precisely magnetic fluxes in the comparator 9 J-OKOB - This configuration of the measuring circuit corresponds; The following state of the circuit-breaker switches; the sub contact; 27 of the first switch 22 is connected to the fixed contact 32; the movable contact 28 of the second switch 23 t is with a fixed contact 33, the movable contact 29 of the third switch 24 is with a fixed contact 34, the movable contact 30 of a fourth switch 25 is with a fixed contact 39, and the movable contact 31 of the fifth switch 26 is with a fixed contact 40 B. In this case, the branch of the measurement object is supplied with power from the first transformer 2 voltage, and the comparison branch from the second transformer 6 voltage, by adjusting the number of turns of the secondary winding 8 of which is equal to eshivanie bridge. With the help of a voltage follower 14 and an additional exemplary measure 16, at the moment of equilibrium, 17 measurements are introduced into the branch of the object, a compensation current 1 c, equal in amplitude but opposite in current

"I

ten

windings 8 of the second transformer 6 p {Apr w, respectively; the number of turns of the secondary main windings 10 and 11 of the comparator, 9 currents; the sum of the resistors 43 and 44.

From ED1) it can be seen that when Z Z, j, the measurement error

I. I

 steam

n -If- (ix IK)

(2)

15 will be small enough. On the contrary, when this limb is noticeable, the measure is extremely difficult to measure.

,

It shows the measurement result

 2x

due to the fact that the current in ve-gvi object

The 20 measurements are determined not by the measured and pedals, but by the parasitic resistance Znap of this branch.

To eliminate the deficiency in the transition to the measurement is enough

The 25 small impedances in the bridge carry out a functional reorganization of the measuring circuit into a configuration in which the equilibration is carried out according to the voltage comparison scheme. Such a configuration is formed thanks to the following state of the switches: the movable contact 27 of the first switch 22 is connected to the failure of the current 1 flowing through 35 ° the movable contact 36, the movable counter of the measurements, resulting in a clock 28 of the second switch 23 — the main windings 4 and 10 transformer with fixed contact 37, movable contact 29 of the third switch 24 - with a fixed contact 38, 40 movable contact 30 of the fourth switch 25 - with a fixed contact 35, and movable contact 31 of the fifth switch 26 o coupled from the fixed contact 40 of the revised 45 breakers.

In this case, a comparison is made.

Ditch 2 voltage and comparator 9 currents, respectively, are de-energized, which is equivalent to eliminating the error from the influence of the parasitic resistances of the branch of the object of measurement. The equilibrium state of the bridge is fixed by the indications of the equilibrium detector 42. Due to the low input resistance of the latter, the current comparator 9 is in the short-circuit mode, which ensures linearization of the balancing lines.

The equilibrium equation of the considered configuration of the measuring circuit is:

. S "-ir" -M)

where t ,, t is the number of turns

the secondary winding 4 of the first transformer 2 voltage and secondary

.two measuring voltages: voltages and, acting on the terminals of the secondary main winding 4,

50 of the voltage transformer 2, and the voltage U, acting on the terminals of the object 17 measurements. The voltage and arises from the flow through the object 17 of the measurements of the current 1, creates

gg with the help of repeater 14. voltage and additional exemplary measure 16; The voltage follower 14 in this case receives power directly from the source 1 of the pit

"I

windings 8 of the second transformer 6 p {Apr w, respectively; the number of turns of the secondary main windings 10 and 11 of the comparator, 9 currents; the sum of the resistors 43 and 44.

From ED1) it can be seen that when Z Z, j, the measurement error

I. I

 steam

n -If- (ix IK)

(2)

15 will be small enough. On the contrary, when this limb is noticeable, the measure is extremely difficult to measure.

,

It shows the measurement result

 2x

due to the fact that the current in ve-gvi object

The 20 measurements are determined not by the measured and pedals, but by the parasitic resistance Znap of this branch.

To eliminate the deficiency in the transition to the measurement is enough

The 25 small impedances in the bridge carry out a functional reorganization of the measuring circuit into a configuration in which the equilibration is carried out according to the voltage comparison scheme. Such a configuration is formed thanks to the following state of the switches: the movable contact 27 of the first two measuring voltages: the voltage and, acting on the terminals of the secondary main winding 4 of the first

50 of the voltage transformer 2, and the voltage U, acting on the terminals of the object 17 measurements. The voltage and arises from the flow through the object 17 of the measurements of the current 1, creates

gg with the help of repeater 14. voltage and additional exemplary measure 16; The voltage follower 14 in this case receives power directly from the source 1 of the pit and via contacts 28 and 37 of the second switch 23, and the first transformer t-arop 2 voltage from the second transformer 6 of the voltage to the secondary winding of which through the contacts 23 and 36 of the first switch 22 connects the primary 3 winding of the first voltage transformer 2. The difference in L. between the voltages Um and Ij, acting at points 47 and 48 of the epithelial circuit, is perceived by a current of 10 current comparator 9, which in this case, due to the disconnected additional resistor 44, works as a transformer wives At the moment {equilibrium of the measuring circuit ip, as a result of which the current through the secondary main

From here

one

„F Zport h к ™ -1z

m, ShogK

(7)

From (7) it follows that the source of error in this case is the parasitic resistance Zjjap current (the branches of the object of measurement, and the value of this error

":, %- (eight)

 o does not depend on the size of the measured

impedance Z, and on the impedance value 15 Z, an additional exemplary measure 16. Since the Z value can be chosen relatively large, it is easy to override the inequality Zn S

Z

About the pairs in which the error in | may be a decrease of 4 of the first transformer 2 by -20 to an acceptable value. By virtue of

the springs do not flow; the parasitic resistance 43 does not affect the accuracy of the measurements. For the same reason, N | e does not affect or resist | 44.

 I In general, the equilibrium equation p | l of this measuring configuration has the form:

constants of values Z „and Z S

steam

25

the error On also becomes a constant and independent of the measured impedance value, due to which

rhenium.

It also follows from (7) that in this configuration of the measuring circuit, the range of measurements of small quantities is not limited to the value of the measured impedance as far as the sensitivity of the equilibrium detector and the permissible energy level of the current 35 flowing through the measurement object, or the voltage occurring at its terminals during the measurement process. In practice, the range of measurement of small impedances in a given measuring circuit as compared to the program can be extended by 3-5 orders of magnitude. Thus, this technical solution, in comparison with a PTUOTOTYPOM, makes it possible to significantly expand the range of measurements of complex resistance in the direction of low impedances and at the same time to increase the accuracy of measurements by introducing

and

t.

- Z,

(3)

It's obvious that

 and.

W (From. Oi

(four)

il

Uk-k

(five)

U ji

supply voltage 1;

the number of turns of the primary windings 3 and 7 of the first 2 and second 6 voltage transformers, respectively; impedance of additional exemplary measure 15; - voltage transfer ratio of the voltage follower 14;

pairs of total parasitic resistance of resistors 46. and 47 branches of reference current.

After substitution (4) and (5) in (3) teach

Z l -

TO

ScSiS

 horn

Zg + Znep

(6)

one

„F Zport h к ™ -1z

m, ShogK

(7)

From (7) it follows that the source of error in this case is the parasitic resistance Zjjap current (the branches of the object of measurement, and the value of this error

":, %- (eight)

 o does not depend on the size of the measured

impedance Z, and on the impedance value Z, of an additional exemplary measure 16. Since the Z value can be chosen relatively large, it is easy to override the inequality Zn S

Z

About pairs at which the error in | can be reduced to an acceptable value. By virtue of

constants of values Z „and Z S

steam

the error On also becomes a constant and independent of the measured impedance value, due to which

rhenium.

It also follows from (7) that in this configuration of the measuring circuit, the range of measurements of small quantities is not limited to the value of the measured impedance as far as the sensitivity of the equilibrium detector and the permissible energy level of the current allows, flowing through the measurement object, or the voltage occurring at its terminals during the measurement process. In practice, the range of measurement of small impedances in a given measuring circuit as compared to the program can be extended by 3-5 orders of magnitude. Thus, this technical solution, in comparison with a PTUOTOTYPOM, allows one to significantly expand the range of measurements of complex resistances in the direction of low impedances and at the same time to increase the accuracy of measurements by introducing

- bridge alternating current of the second shoulder transformer of the auxiliary voltage of the 11th resistor and five switches, with the help of which the functional reorganization of the measuring circuit and configuration is carried out, with

5 which equilibration occurs in the current comparison circuit, in a configuration where equilibration occurs in the voltage comparison circuit.

Claims (1)

Claims of the invention An alternating current transformer bridge for measuring the impedance parameters, comprising a power source, the first terminal of which is connected to a common bus, the main and auxiliary measures, the first voltage transformer. 14553248 the voltage formatter is directly, and the first primary output winding of the first voltage transformer through g movable and fixed contacts of the first switch are connected to the second output of the power source, to which the primary output of the primary winding is also connected through the movable and fixed contacts of the second switch the repeater is directly connected to the common bus by comparing, while the second fixed the contacts of the first and second switches and the first output of the main exemplary measure are connected to the first 15 output of the secondary winding of the second voltage transformer, the second output of which and the second output of the primary winding, as well as the second fixed contact of the third switch-20 body are connected to the common bus bridge, the second outputs the primary and secondary standard measures are connected respectively to the moving contacts of the third and fourth switches, while the second fixed contact of the third switch is connected to the main the second winding; the main windings of the current comparator, the fixed contacts of the fourth switch are connected respectively to the terminals of the auxiliary windings of the current comparator, the moving contact of the fifth switch and the first terminal of the mode resistor are subcurrent, the currents, the first terminals of the main windings of which are connected respectively to the main potential and current terminals for connecting the measurement object, and the second terminals are interconnected, the first terminals of the auxiliary windings are connected respectively to the auxiliary power potential and current terminals for connecting the measurement object, the second auxiliary winding output of the first voltage transformer and the second output of the second main current comparator winding are connected to the common busbar bridge, the voltage follower, the output of which is connected to an additional exemplary measure, equilibrium detector , the first output of which is connected to the first output of the output winding of the current comparators and with a common bus, characterized in that, in order to extend the measurement range in the direction of small impedance In addition to the accuracy of measurements of these quantities, a second voltage transformer, five switches and an additional resistor are entered into it, the first is connected to the second output of the output winding of the current comparator, and one of the fixed contacts of the fifth switch and the second output are added to resistor connected to the second  - t K. “bv. S V-WCM iriCnDi U IS I waters of the primary winding of the second trans equilibrium detector. The contacts of the first and second switches and the first output of the main exemplary measure are connected to the first 15 output of the secondary winding of the second voltage transformer, the second output of which and the second output of the primary winding, as well as the second fixed contact of the third switch 0 are connected to the common busbar of the bridge; the main and additional standard measures are connected respectively to the moving contacts of the third and fourth switches, while the second fixed contact of the third switch is connected to the first Much of the second; main winding of the current comparator, fixed contacts of the fourth switch are connected respectively to the terminals of the auxiliary winding of the current comparator, the movable contact of the fifth switch and the first output of the mode resistor are connected to the second output of the output winding of the current comparator, and one of the fixed contacts The fifth switch and the second output of the additional resistor are connected to the second  - t K. “bv. S V-WCM iriCnDi U IS I About the detector equilibrium detector.