SU69367A2 - Bridge for measuring impedances in absolute value and angle - Google Patents

Description

In many areas of electrical engineering and, in particular, in wired communication, it is necessary to measure impedances. In this case, in most cases, the aim is to determine the absolute value (modulus), the angle and the sign of the angle of the resistance being measured.

For the most part, these measurements are made by means of bridge circuits, which allow the determination of the active component and the capacitance or inductance, which determine the reactive component of the measured resistance. The absolute value of the resistance, the angle and the sign of the angle are further calculated using special formulas, which are different for each type of bridge.

The unbalanced bridge circuit is known (see N. N. Soloviev. "Electrical measurements in wire communication, 1938, p. 94), which allows to determine the absolute value and angle of the measured resistance. However, this method of measurement did not resolve the issue of determining the sign of the angle, and it is difficult to determine the absolute value of the resistance and angle by gradual comparison of the stresses, which extremely limits the scope of application of this bridge circuit.

The present invention proposes a bridge circuit allowing measurement of the absolute values of resistance and angle by means of a zero differential indicator, and the angle sign by means of a bridge pointer of the phase shift sign according to the method constituting the subject of the main copyright certificate No. 69368. The method for determining the phase shift angle by this copyright certificate is based on the use of an unbalanced AC bridge composed of three active and one reactance, and is that the bridge indicator is switched from the diagonal of the latter to the voltage under study through the active arm of the bridge and the sign of the angle is determined by the indicator deviation.

According to the present invention, a chain of 166 is connected to the power points of the bridge.

valuable equal to the modulus of active and reactive resistances and between the common point of these resistances and the common points of resistance in the two branches of the bridge is switched on by means of a switch, an electrical measuring instrument, so that the sign of the phase shift can be judged by the changes in the instrument readings when the switch one position to another.

To measure the absolute value of the resistance and the magnitude of the phase shift angle, such a device provides for the use of a differential zero indicator.

FIG. 1 and 2 are schematic versions of the proposed device.

In the embodiment of FIG. 1, in addition to the phase shift indicator indicator, a differential indicator comprising two identical amplifiers, two identical detectors and a logometer is used.

The bridge is formed by three active resistances I, R, R and measured resistance Zx.

The index of the sign of the phase shift is composed of three active resistances,,, and reactive C; The indicator of the pointer is a switch device DG (detector galvanometer), switched by means of switch K.

For measurements on this scheme should be provided

AO

(оС

The FG device is connected to the point of the circuit.

To measure the absolute value of the resistance, the differential indicator is connected to points a, d, b; changes once to get a zero reading on the scale of the logometer; in this case

171 Р

I x I - A

To determine the angle of the measured resistance, the differential indicator is connected to the points e, c, d;

here .2 arctg -.

The sign of the angle is determined by switching the detector galvanometer to point d; an increase in readings indicates a predominance of inductance in the reactive component of the measured resistance, a decrease in readings indicates a predominance of capacitance. The DG scale can thus have three marks: (-) LO), (+).

In some cases, the requirements for determining the accuracy of determining the angle are small and then the angle sign pointer can be used simultaneously as a gauge for the absolute value of the angle.

For these cases, it is possible to use the circuit of FIG. 2. Let here

conditions are: R Z; R -.

Then, at L / 1 const, the voltage U is a measure of the magnitude and sign (рх Of course, there are options with checking the phase shift indicator and adjusting its sensitivity with alternating voltage at the input of the bridge.

Subject invention

Claims (2)

1. A bridge for measuring impedances in absolute value and angle, made according to the type of unbalanced bridge, characterized in that, in order to determine the sign of the phase shift by the method of copyright certificate No. 69368, a chain of successively connected in series with the module is attached to the power points of the bridge and reactance and between the common point of these resistances and the common resistance points in the two branches of the bridge, the electrical measuring instrument is switched through the switch so that the sign of the phases The new shift could be judged by changes in the instrument readings when the specified switch is moved from one position to another. 2. In the bridge of claim I, the use of a differential zero indicator to measure the absolute value of the resistance and the magnitude of the phase shift angle. Ki FIG. 2  - -L- j Uekligs / cd amplifiers I I I 1I 1 , Af gelgvr I Dgte mountains / | I II.D.N. U 1 J AxfCPSHU. HHuUmTOP