SU1539670A2 - Transducer of d.c. and a.c. - Google Patents

Abstract

The invention relates to electrical measurements and can be used to convert signals proportional to direct and alternating current, with the provision of galvanic isolation. Purpose: improvement of conversion accuracy. The DC and AC sensor contains transformers 1 and 4 with the same transformation ratios, differential amplifiers 2 and 7, resistors 3,5,6 and 8, large-scale converter 9. Differential amplifier 2 together with the secondary winding of transformer 1 and resistors 3,5, 6 forms an auto-oscillator that generates a rectangular alternating voltage. In addition, an operational amplifier 10, an integrating circuit 11 and new functional connections are additionally introduced into the sensor, as a result of which the variable signal is compensated for in the output signal of the sensor with the frequency of the oscillator. 2 Il.

Description

Thebes 1

The invention relates to electrical measurements, can be used to convert signals proportional to direct and alternating current, with the provision of galvanic isolation and is an improvement of the device according to ed. W 1265628.

The purpose of the invention is to improve the accuracy of the conversion by compensating for the variable component of the sensor output with the frequency of the oscillator.

FIG. 1 shows the electrical circuit of the sensor; in fig. 2 - diagrams - 1 frames, which explain his work.

The current sensor (Fig. 1) contains a transformer 1, the beginning of the secondary winding of which is connected to the output of the differential amplifier 2 and one output, 2 house of the resistor 3, and the end with the beginning of the secondary winding of the transformer k and simultaneously with the inverting input of the differential amplifier 2 and with one output resistor b. The second pin 2 of the resistor 3 is connected to the non-inverting input of the differential amplifier 2 and to one pin of the resistor 6, the second pin of which is connected to the common bus, to which the second J pin of the resistor b is also connected. The end of the secondary winding of the transformer k is connected to the inverting input of the differential amplifier 7 and to one output of the resistor 8, the second output of which is simultaneously connected to the output of the differential amplifier 7 and to the input of the large-scale converter 9, the output of which is connected to the non-inverting input of the differential amplifier}. The current sensor also contains an operational amplifier 10, the first input of which is connected to the output of the differential amplifier 7, and the output is connected to the output terminal of the sensor, and an integrating circuit 11, the input of which is connected to the combined terminals of the secondary windings of transformers 1 and k, and the output connected to the second input

power amplifier 10. The primary windings of transformers 1 and k are connected in series in accordance with and are intended to be connected to a controlled current circuit.

The device works as follows.

Differential amplifier 2 together with transformer 1 secondary winding and resistors 3, b and 6 obra

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five

0

five

An auto oscillator is used. In the absence of a controlled current in the primary windings of transformers 1 and C, the mode of operation of the oscillator is symmetric, since in this case there is no biasing of the magnetic cores of the transformers 1 and k with a controlled current. In this case, an alternating voltage UA of a rectangular shape (Fig. 2) is applied to the secondary winding of the transformer 1, and a magnetizing current i flows through this winding (Fig. 26). This current creates a voltage drop across the resistor 5, which is applied to the input of the differential amplifier 7 through the secondary winding of the transformer 4, causing the appearance of alternating voltage at the output of the generator and the frequency of the oscillator (Fig. 2c). The amplitude of this voltage is limited by the inductance of the secondary winding of the transformer C, but cannot be zero, since the winding has a finite inductance. At the same time, the same voltage drop across the resistor 5 proportional to the current 1M of magnetization is fed to the input of the integrating circuit 11, the output of which also has alternating voltage U (frequency of the oscillator (Fig. 2d), and the form of this voltage almost coincides with the form The output voltage of the differential amplifier 7a is opposite to the phase. Therefore, after summing these voltages by the operational amplifier 10, the variable frequency of the oscillator is formed at the output of the operational amplifier 10, i.e. The output of the sensor is reduced by a factor compared with the prototype (Fig. 2d). When a controlled direct or alternating current flows through the primary windings of transformers 1 and k, it appears proportional to its constant or variable component and in the secondary windings of the transformers. For a constant component (or a variable that flows simultaneously in the primary and secondary windings), the secondary winding of the transformer k is a small resistance. At the same time, the current flowing through the secondary winding of the transformer A and the resistor 8 causes the appearance at the output of the differential amplifier 7 of a voltage equal to sum

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Claims (1)

Formula of the invention Sensor of direct and alternating current according to ed. Ν '1265628, wherein, in order to increase the conversion accuracy, an operational amplifier and an integrating circuit are additionally introduced into it, moreover, the first input of the operational amplifier is connected to the output of the second differential amplifier, the second input of the operational amplifier is connected to the output of the integrating circuit, the input of the integrating circuit is connected to the inverting input of the first differential amplifier, and the output of the operational amplifier is connected to the output terminal: