SU659964A1 - Phase method of balancing ac bridge - Google Patents

Description

that in the indicated difference in phase angles, when adjusting the balancing element, only one angle changes, namely the phase angle formed by the vectors of two voltages, one of which is unbalance stress, and the second is the voltage drop across the shoulder protruding the shoulder, containing the measured complex is resistive, which reduces the effectiveness of the differential comparison method, thereby reducing the sensitivity of the bridge circuit to changes in the measured parameter.

In addition, this method has a significant drawback that means all methods of separate balancing, namely, the need to shunt the shoulders of the bridge circuit, so this method does not have a sufficiently high accuracy, since the measurement result includes the error from shunting the helix.

The aim of the invention is to increase the sensitivity in the 1st spine.

The goal is achieved by the fact that in the phase balancing method of a non-alternating current bridge, consisting in the formation of a regulating action for separate balancing of the metering measuring circuit by comparing additional signals, proportional to the phase angles between the voltages taken from the bridge measuring circuit, form the first additional signal lower the voltage of the power supply of the measuring measuring circuit, form the second additional signal proportional to the vector difference For the unbalance voltage and the first additional signal, a third additional signal is formed, which is proportional to the time interval, the beginning of which is with the transition point through zero from minus to plus (from plus to minus) the voltage psbalance, and the end coincides with the nearest transition point through zero. from minus to plus (e plus to minus) of the first additional signal or time interval, the beginning of which coincides with the point of transition through zero from minus to plus (from ilus to minus) of the first solitary signal and the end coincides with the nearest point of transition through zero from minus to plus (from plus to minus) unbalance voltage, form a quarter-third additional signal with a duration proportional to the time interval, the beginning of which coincides with the transition point through zero from min) to plus (with plus to minus) of the second additional signal, and the end coincides with the nearest point of transition through zero from minus to plus (from plus pa minus) unbalance voltage, or time interval, the beginning of which coincides with the point of transition through zero from minus and the plus (from plus to minus) voltage unbalance, and the end coincides with the nearest point of transition through zero from minus to plus (from plus to minus) of the second additional signal, form the fifth additional signal proportional to the difference of the third and fourth additional signals, and The regulating effect necessary to equilibrate the bridge measurable value to the state of quasi-equilibrium by the measured component of the complex analog signal is formed by the sign of the fifth additional signal.

The formation of the first additional signal equal to the voltage of the bridge measuring circuit halved and the second additional signal proportional to the vector difference of the unbalance voltage and the first additional signal increase the sensitivity by eliminating the error from shunting the shoulders of the bridge measuring circuit, and the formation of the third and fourth additional signals allows to significantly increase the sensitivity, since changing the balancing elements The second and fourth additional signals change in mutually opposite directions (as one signal decreases, the second increases and vice versa).

FIG. 1 shows a device that implements the proposed method; in fig. 2 is a topographic diagram of the equilibration process of a bridge measuring circuit for measuring the reactive component of the complex resistance, where b is the supply voltage of the bridge measuring circuit;

dc is the unbalance voltage of the bridge measuring circuit; do - halved voltage pptann;

 and Ci is the measured complex resistance;

R, is an adjustable model element that serves to balance the reactive component of the complex resistance;

RS, Ci, - exemplary irregular punctures

I

elements, and s C1 4

"1" 2, p are the equalization circles in generalized notation;

d is the position of the potential point of the top of the bridge branch, not containing the measurable impedance when the condition Jc4 is fulfilled

Co, Ci, Cz are the posmol positions of the potential point C of the vertex of the branch of the bridge containing the measured impedance; Ф is the phase angle between the dc and do voltages; t | z is the phase angle between the dc and dc - do voltage, provided that 2do ab. It can be shown that at the point where the point C comes out to the surrounding p (Fig. 2), the equality

- Oh, (1

since f and oj; are angles at the base of an isosceles triangle dCo, and,.

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

o-.0, (2)

which corresponds to a non-equilibrium (re-equilibrium) over the reactive component of the measured complex resistance.

In the event that a potential point C occupies the position of point C in a pie chart, then equality (1) is violated in the other direction.

, (3)

which corresponds to a state of non-equilibration (underbalancing) in the reactive component of the measured impedance.

Thus, the sign of the left part of expression (1) carries complete information about the position of the potential point C of the bridge relative to the quasi-equilibrium state, i.e. through the potential point d.

The described method can be implemented, for example, using the device shown in FIG. one.

The device contains matching devices 1 and 2, difference circuit 3, amplifiers-limiters 4-6, elements “prohibition 7 and 8, integrator 9.

A nanosecond balance Udc is fed through matching device 1 to the input of amplifier-limiter 4 and to one of the inputs of the difference circuit 3, to the second input of which voltage-f arrives at the same time to input of the amplifier-limiter 6. Reinforced and the limited signal from the output of the amplifier-reader 4 and the inverse inputs of the elements "prohibition 7 and 8. A differential signal is fed to the signal input of the element through the amplifier-limiter 6

the signal f / oc, and the signal input of the element "prohibition 8" is given an amplified and limited signal from the output of Ssintnel limiter 4. The signal from the output of the element "pre5 7, the duration of which is proportional to the phase angle d), is fed to one of the inputs of the integrator 9, to the second input of which the signal from the output of the element "prohibition 8, the duration of which

0 is proportional to the angle f. The polarity of the signal from the output of the integrator 9 carries complete information about the relative angles φ and.

The use of the proposed phase method of separate equalization

5 ac bridge provides but

in comparison with existing methods

separate balancing next

advantages:

the possibility of forming a regulatory action using only the unbalance voltage and the supply voltage of the bridge measuring circuit, which will allow us to simplify the implementation of the law;

5 the possibility of increasing the equilibrium due to the exclusion and warmth of the shunt of the transmission bridge; precision due to differential

0 Comparison of pre-exciter signals, iroportional phase angles, psmen juxtams in different directions.

F o rmu l invention

The phase method of balancing the bridge with non-transitory current, which consists in forming a regulating effect for the separate balancing of the bridge measuring circuit due to the comparison of non-violent signals proportional to the phase angles of the bridge on the counter, in order to accomplish a task. The signal is equal to the doubling of the thread of the measuring circuit, the second additional signal is formed by the proportional said secondary raznoeti nanr l tim unbalance and the first additional sngnala form a third duration of an additional signal proportsnonalnoy time interval, the beginning of which

coincides with the zero crossing point from minus to zero (from ilus to minus) of unbalance, and the end coincides with the shortest non-transition point through zero from minus to zero (from plus to minus) of the first additional signal or time interval, the beginning of which coincides with transition point through zero from minus to plus (from plus to minus) of the first additional signal, and the end coincides

with the nearest crossing point with zero

minus by plus (from plus to minus) unbalance voltage, form the fourth additional signal of duration proportional to the time interval, the beginning of which coincides with the point of zero crossing from minus to plus (from plus to minus) of the second additional signal, and the end coincides with the nearest point of transition through zero from minus to plus (from plus to minus) unbalance voltage, or time interval}, the beginning of which coincides with the point of transition through zero from minus to plus (from plus to minus) unbalance voltage, and the end flushes with the nearest zero crossing point from minus to plus (from plus to minus), the second additional signal.

form the fifth additional signal proportional to the difference of the third and fourth additional signals, and the regulating effect required for

bringing the bridge measuring circuit into a state of quasi-equilibrium by the measured component, and its impedance is formed by the sign of the fifth additional signal.

Information sources,

taken into account in the examination

1.Karandeev K. B., Stamberger G. A. Obobsh, Enna theory 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 number 384072, cl. G 01R 17/10, 1973.

with,

ft

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