SU731386A1 - Phase method of balancing ac bridge - Google Patents

Description

when adjusting the balancing element, only one angle changes, namely the phase angle, created by two voltage vectors, one of which is the unbalance voltage, and the other is the voltage drop across the shoulder opposite the shoulder containing the measured complex resistance , which reduces the efficiency of the differential comparison method, thereby reducing the sensitivity of the bridge circuit to changes in the measured parameter.

The goal of true isooorientation is to increase sensitivity.

This goal is achieved by the fact that in the phase method of separate balancing of the AC bridge, which consists in forming a regulating action for separate balancing of the bridge measuring circuit, the additional signal proportional to the phase angles between the voltages reduced from the bridge measuring circuit is formed duration, proportional to the time interval, the beginning of which coincides with the point of transition through zero from minus to ilus (with sa to minus) unbalance voltage, and the end coincides with the nearest point of zero crossing from minus to plus (from plus to minus) voltage of the apex of the additional branch (center of equilibration of the branch not containing the measured impedance) relative to the top of the bridge branch, not containing a measurable impedance, or a time interval, the beginning of which coincides with the point of transition through zero from minus to plus (from plus paumius) of the top node of the additional branch, and the end coincides with the nearest point transition through zero from minus to plus (from plus to minus) unbalance voltage, form the second additional signal of duration proportional to the time interval, the beginning of which coincides with the point of transition through zero from minus to plus (from plus to minus) the voltage of the apex of the additional branch (the center of the circle balancing the branch that does not contain the measured impedance) relative to the top of the bridge branch containing the measured impedance, and the end coincides with the nearest point of transition through zero from minus to plus (from plus to minus) of unbalance voltage, or a time interval, the beginning of which coincides with the point of transition through zero from minus to ilus (from plus to minus) of unbalance voltage, and the end coincides with the nearest point of transition through zero c minus to plus (from plus to minus) of the voltage of the additional branch, relative to the top of the branch of the bridge containing the measured impedance, form the third additional signal proportional to the difference between the first and second additional signals, and the regulating effect The type required to bring the bridge measuring circuit into a state of quasi-equilibrium in the measured component of the impedance is formed by the sign of the third additional spgnal.

The formation of the first and second additional sigals allows a significant increase in sensitivity, since, as the uranium-hanging elements change, the first and second additional signals change in opposite directions (as one decreases, the second increases, and vice versa).

ha fig. 1 image device that implements this method; in fig. 2 is a topographical diagram of the equilibration process of a bridge measuring circuit for measuring the reactive component of the impedance, where; Ri, Ci - measured complex resistance;

Kg, R4 - adjustable model elements that serve to balance the reactive component of the complex resistance and the component proportional to tg6;

RS. C4 - exemplary unregulated elements;

cd - nair unbalance; ab - nutritional deficiency;

«I2, (3 - equilibration circumferences in general, 1);

bo, 6i C2, d - possible positions of the noticeable points of the vertices of the bridge c and d; φ is the phase angle between the voltage do and dc;

φ is the phase angle between the jumpers and the dc and wasps.

At the moment when the point with the circle | 3 (Fig. 2) s equals

 f-1 | s 0, (1)

since φ and z} are the angles at the base of the isosceles triangle dco, and od oc.

If, for example, the potential point from the bridge occupies the position Ci in the pie chart (Fig. 2), then equality (1) is violated in one direction

f- |) 0 ,. (2)

which corresponds, for example, to a non-equilibration (re-equilibration) along the reactive component of the measured com- itilex resistance.

Thus, the sign of the left side of expression (1) carries complete information about the position of the potential point from the bridge relative to the quasi-equilibrium state, then

there are states of quasi-equilibrium bridge

The reactive component of the measured complex impedance is reached at the moment when the potential point c is drawn to the circle p passing through the potential point d.

The device contains matching devices 1-3, limiting amplifiers 4-6, elements 7, 8 “Prohibition, integrator 9.

Voltages Udc, ai, oo. matching devices 1-3 are fed respectively to the inputs of limiting amplifiers 4-6. From the output of limiting amplifiers 4 and 6, signals are sent respectively to the signal inputs of elements 7, 8 "Prohibition. The signal from the output of element 7" Prohibition, whose duration is proportional to the phase angle r | ), is applied to one of the inputs of the integrator 9, to the other input of which the signal comes from the output of element 8 "Inhibit, and its duration is proportional to the angle φ. The polarity of the signal from the output of the integrator 9 carries unambiguous information about the relative angles φ and | |).

The use of the proposed phase method of separate balancing an AC bridge provides a high sensitivity compared to existing methods of separate balancing.

Claims (2)

1. Karandeev, K. B., Stamberger, G. A. “Generalized theorem of bridge circuits of alternating current. Ed. Siberian Branch of the USSR Academy of Sciences, Novosibirsk, 1961, p. 124-126. 2. USSR author's certificate LGO 384072, cl. G 01R 17/10, 03/25/71.