SU748255A1 - Digital ac bridge - Google Patents

Description

. The invention relates to electrical measuring equipment and can be used to measure impedance parameters. A digital AC bridge is known, containing a sinusoidal voltage generator included in the supply diagonal of the measuring bridge, the first vertex of whose measuring diagonal, adjacent to the measured complex resistance, is connected to the first inputs of the first and BTOpioro phase shifters and the second input of the phase phase converter transform, l, the first vertex of the diagonal of the pit. VIA, adjacent to the measured complex resistance, is connected to the first input of the third phase-time transducer and the third inputs of the first and fourth phase transducers ,; the top of the power diagonal is connected to the second input of the first phase converter, to the third inputs of the second and third phase converter and to the first input of the fourth phase converter, the first and second outputs of the first phase converter are connected respectively to the first inputs of the first and second integrator, the second inputs of which are connected to the output of the second phase converter, the outputs of the first and second integrators are connected respectively to the direct and inverse at the inputs of the Prohibition element, the output of which is connected to the input of the first display unit through the reactive component of the measured impedance, the outputs of the third and fourth phase-time converters are connected to the first and second inputs of the third integrator, respectively, through the tangent control unit the loss angle of the measured impedance is connected to the input of the second display unit 1. . The disadvantage of this bridge is the low sensitivity of the balancing of the loss angle of the measured complex resistance with respect to the tangent, due to minor changes in the signal generated in the path of the formation of regulatory influences from changes in the balance parameter.

In addition, this bridge has low accuracy, due to the fact that such a structure of the digital AC bridge does not allow the formation of signals used to form regulatory influences in both balancing channels.

A digital AC bridge is known, comprising a sinusoidal voltage generator, included in the supply diagonal of a bridge measuring circuit, the first of which has a diagonal connected to the measured impedance, connected to the nepauNi inputs of the first and third phase-to-phase converters and the second input to the second phase-time converter, the second, the top of the measuring diagonal of the bridge circuit is connected to the third input of the second phase-time transformed, the first top of the The power supply of the bridge measuring circuit, connected to the measured coillex resistance, is connected to the Third input of the first phase-to-phase converter and the first input of the phase-shifting circuit, the second vertex of the power supply circuit is connected to the second input of the first phase of the temporary converter, to the first input of the phase-shifted circuit, connected to the second input of the phase of the temporary converter, to the second input of the phase-shifting circuit; phase transformer and the second input of the façade circuit, the output of which is connected to the second current of the third phase transform ate, first and second outputs of the first fazovremennogo converter connected respectively to the first inputs of the first and second integrators v.yhod fazovremennogo second transducer connected to the inputs of four integrators vtorzm; The first and second outputs of the third phase converter are connected, respectively, to the first inputs of the third and fourth integrators, the outputs of the first and second integrators are connected, respectively, to the direct and inverse inputs of the first element. The output of which is prevented through the balance block by measuring the integrated impedance connected to; the input of the first block indication, the outputs of the third and fourth inputrs are connected, respectively, to the direct and. the inverse input of the second element of the Inhibit, the Kdroporo output through the balance unit by the active component of the measured impedance with connected to the input of the second display unit 2.

The disadvantage of this mrsta is the low accuracy of the balancing channel along the active component of the measured, complex resistance, due to the presence in the channel of the differentiating circuit,

748255

error in the process of forming regulatory actions, as a result of which the accuracy of the opreceloni tangent of the loss angle of the measured co-shlex resistance based on the measured active and reactive components of the complex resistance will be obviously low due to the low accuracy of the measurement of the active component of the measured complex resistance

The purpose of the invention is to improve the accuracy of measurement of the parameters of the complex resistance.

This goal is achieved by the fact that in a well-known digital ac bridge containing a sinusoidal voltage generator included in the diagonal of the bridge measuring circuit, the first vertex of the diagonal of the supply, which is adjacent to the measured impedance, is connected to the first input of the first phase-time converter, The second vertex of the diagonal power supply of the bridge measuring circuit is connected to the second input of the first phase-to-phase converter and the first input of the second, phase-dependent transducer. the developer, the first vertex of the measuring diagonal of the bridge measuring circuit, adjacent to the measured impedance, is connected to the third inputs of the first and third phase-to-phase converters and the second input of the second phase-to-phase converter, the second top and the measuring diagonal of the bridge measuring circuit is connected to the third input of the second phase-time transformer; The first and second outputs of the first phase converter are connected to the first inputs of the first and second integrator respectively, the output of the second phase shifter is connected to the second inputs of four integrators, the first and second outputs of the third phase shifter are connected to the first inputs of the third and fourth integrators, respectively, the output of the first integrator is connected to the forward input of the first Ban element, the inverse input of which is connected to the output of the second integrator, the outputs of the third and fourth integrators are connected respectively to the direct and inverse inputs of the second element Prohibition, output the first element of the prohibition through the balance of the reactive component of the measured impedance of the complex impedance connected to the first display unit, the output of the second element of the prohibition through the unit of balancing the loss tangent of the measured impedance connected to the input of the second display unit, the second vertex of the measuring diagonal bridge measuring circuit connected to the first input of the third phase-to-phase converter, the first top of the diagonal of the power of the bridge measuring circuit and to the second input of the third F zovremennogo converter. The elimination of the differential circuit from the path of equilibration by the loss tangent increases the accuracy of the measurement of the loss tangent, and accordingly the component of the measured impedance, which is determined by the measurement of the reactive component and the loss tangent, can be calculated from accuracy .. FIG. 1 shows a block diagram of the proposed device; FIG. 2 and 3 are topographic diagrams of the process of balancing a bridge measuring circuit along the reactive component of the measured impedance and the loss tangent, respectively; in fig. 4-9 are time diagrams for the operation of the device. FIG. Figures 4-6 illustrate the operation of the balancing channel in terms of the reactive component of the measured impedance, and in FIG. 4 shows the case when the angle is greater than the angle Ч and + 180, i.e. point c in the pie chart of fig. 2 is in zone 1. FIG. 5 presents the case when the angle Φ is greater than the angles S- and 4 + 180, i.e. Point C is in the 2nd zone (FIG. 2), and FIG. 6 - the case when the angle F is greater than the angle H, but less than the angle H + 180 °, i.e. point C is in the 3rd zone of the pie chart of FIG. 2. FIG. 7 to 9 show the three positions of point c in the pie chart of FIG. 3 and the operation of the balancing channel in terms of the loss tangent of the measured impedance is elucidated. FIG. 7 shows the moment when the angle φ is greater than the angles V and U + 180 (point C lies in the 1st zone of Fig. 3). FIG. 8 shows the moment when the angle F is less than the angles and V + (point C in the 2nd zone of Fig. 3). And in FIG. 9 shows the case when the angle H is greater than the angle V, but less than the angle V + + 180 (point C in the 3rd zone of Fig. 3). The device (Fig. 1) contains a bridge measuring circuit 1, in which the measured impedance 2, 3 (C-1, R-,), model element 4, which serves to select the limits (Rj), adjustable sjjeMeHT 5, which serves to balance reactive component (adjustable element b, which serves to balance loss tangent (R), exemplary unregulated element 7 (C)), sinusoidal voltage generator 8, phase-time converters 9, 10, 11, integrators 12, 13, 14, 15, elements 16, 17 Prohibition, balance block 18 by reactive composition the measured complex resistance to it, the tangent of loss angle balancing unit 19, indication blocks 20, 21, and the sinusoidal voltage generator 8 is included in the diagonal gauge of the bridge measuring circuit 1. The first vertex of the diagonal of the supply L of the bridge measuring circuit 1, Adjacent to the measured impedance 2, 3 is connected to the rtep input of the phase-time converter (FVP) 9 and the second input of the FPP 11. The second top of the power diagonal is connected to the second input of the FPP 9 and the first input of the FPP 10. Lever to the top C The measuring diagonal ccL, adjacent to the measured impedance 2, 3, is connected to the third FVP 9 and FVP 11 and second FVP 10 inputs. Second ve (Hyina's measuring diagonal is connected to the third FV 10 input and the first input of the FVP 11. First and second the outputs of the FPP 9 are connected to the first inputs of the integrators 12, 13, respectively. The output of the FPP 10 is connected to the second inputs of the integrators 12, 13, 14, 15. The first and second outputs of the FPP 11 are connected to the first inputs of the integrators 14, 15, respectively. The outputs of the integrators 12, 13 are connected respectively to the direct and inverse inputs of the Bar 16 element, the output of which is connected through the reagent component of the measured impedance through the balance unit 18 to the input of the display unit 20. The outputs of the Integrators 14, 15, are connected respectively to the direct and inverse inputs of the element 17 Ban, the output of which through the block 19 of balancing by loss tangent is connected to the input of the block 21 of the display. FIG. 2 and FIG. 3 shows the voltage La of supplying the bridge measuring circuit; unbalance bridge voltage dc; measuring circuit; voltage b c removed from the shoulder of a bridge circuit, which includes an exemplary element 4, serving to select limits (R2) voltage bd, removed from the shoulder of a bridge measuring circuit, which includes an adjustable element 5, balancing a bridge circuit with reactive co. (Rj), ad voltage taken from the shoulder of the bridge circuit, which includes an exemplary unregulated element 7 (C) and an adjustable element 6 (R), angle H formed by the voltage vectors b a and bd, angle formed by stress vectors bc and dcj angle, obezovanny vector ramma stresses la and ad; circumference rt, f) balancing the backbone of the measuring circuit in generalized designations.

The process of balancing a bridge measuring circuit by the reactive component of the measured impedance is carried out by adjusting the variable parameter of the element. 4 (R2). The bridge circuit 1 (Fig. 1) is located in a state of quasi-equilibrium along the reactive component of the measured impedance, if the potential points c and d corresponding to the vertices of the measuring diagonal are located on the same circle. The information necessary for switching the parameter balancing the bridge circuit along the reactive component is obtained by simultaneously comparing the angles V and H + IBO with the angle S. This makes it possible to determine exactly which of the three possible zones (1st, 2nd or the 3rd) pie chart (Fig. 2) is point C. From the analysis of the pie chart, it can be seen that in the case where the potential point c is in the 1st zone, the angle is greater than the angles H and H + 180. In the 2nd zone, the angle S is less than the angles. H and H +. In the 3rd zone, the angle is greater than the angle S, but less than the angle H + 180 °.

Balancing the pavement measuring circuit by the loss tangent will be achieved when the points c and d are located on the same circle c74. In order to obtain unambiguous information about the location of point C in one of the possible zones (1, 2 or 3 of Fig. 3), the simultaneous comparison of the angles V and + 180 with the angle φ is carried out. Analysis of the circular diagram (Fig. 3) shows that if the point C is in the 1st zone, the ANGLE is greater than the angles V and V + 180 .. In the 2nd zone, the angle S is smaller than the angles) and V + 180.AB 3- In this zone, the angle is greater than the angle V, but less than the angle + 180.

The operation of the digital bridge reduces to simultaneously balancing the bridge circuit by the loss tangent and reactive component of the measured impedance, carried out by two balancing channels.

Consider a path of formation of regulatory actions, consisting of phase-time converters 10, i4 of integrators 14, 15, element 17

The prohibition, which, together with the balancing unit 19, the display unit 21, forms a balancing channel in terms of the loss tangent of the measured complex resistance.

The channel is operated as follows.

Voltages and voltage taken directly from bridge circuit 1,

enter the phase converter 10, and the voltage Uad and the input phase converter 11 (Fig. 7-9, line a) Phase-time converters 10, 11 produce pulses of the same amplitude (Fig. 7-9, row b, c, d) whose duration corresponds to the phase angles between the voltages supplied to their inputs. On the first and second outputs of the phase-time converter 11, two pulses are produced, corresponding to the angles V (Fig. 7-9, line c) and V + 180 (Fig. 7-9, line d). At the input of the phase converter 10, a single pulse is produced, the duration corresponding to the phase angle H (Fig. 7-9, line c). The impulses from the outputs of phase-time converters 10, 11 are fed to the inputs of the integrators D4, 15. The integrator 14 compares the angles S and) (Fig. 7-9, line e), and the integrator 15 - the angles V + 180 ° (Fig. 7-9 line f).

The polarity of the signals at the outputs of the integrators 14, 15 depends on the ratio of the values of the phase angles and,

If and + 180. The signals at the outputs of the integrators 14, 15 will be of the same polarity if the phase angle is appropriate or less than the phase angles) and V +180 (Fig. 7, lines e / f), or more than the phase angles N) and Vf 130 ° (Fig. 8, lines e, f). The signals at the outputs of the integrators 14, 15 will be equipolar if the phase angle P is greater than the phase angle 1), but smaller than the phase angle V + 18 (7 (Fig.9, lines e / f)

From the outputs of integrators .4, 15, the signals are fed to the inputs of element 17 Ban, the signal from the output of which controls the work of balance tangent 19 of the loss angle of the measured impedance. Only when from integrators 14, 15 to element 17 Ban biased signals are received; at the output of element 17, the prohibition will be the presence of a signal, for example, a positive polarity.

Blocking (dropping) all changes of the adjustable element 5, balancing the bridge measuring circuit by the tangent of the loss angle, leading to no signal at the output of the element 17 Prohibiting and dropping (blocking) all changes of the adjustable element 5 leading to the presence of a signal at the output of the element 17 The prohibition of balancing the bridge measuring circuit according to the loss tangent of the measured impedance.

Simultaneously with the balancing of the loss tangent, the balancing of the reactive component occurs kytsey. The balancing channel in this case is formed by the path of formation of regulatory actions, which contains phase-time converters 9, 10, integrators 12, 13 elements 16 of the Inhibit and an equalization unit 18 by the reactive component, the display unit 20.

The operation of this part of the flowchart npio is similar to the work of the balancing channel according to the loss tangent-angle. The difference lies in the fact that the phase angle is compared with the phase angles H and S + 180 ° (Fig. 4-6).

The use of the proposed digital ac bridge provides, in comparison with existing bridges, an increase in the accuracy of measuring the loss tangent of the measured impedance, and hence the active component of the measured impedance.

Claims (2)

1. USSR author's certificate 384072, cl. G 01 R 17/10, 1974. 2. Prokuncey A. F. and others. Digital bridge AC current. Instruments and control systems, 1977, 11. H about xt.  H "