SU1541520A1 - Device for measuring direct current - Google Patents

Abstract

The invention relates to electrical measuring equipment and can be used to measure direct current. The purpose of the invention is to simplify the device and improve the measurement accuracy. The device contains an operational amplifier 1, a magnetic circuit 2, covering the conductor 3 with a controlled current, windings 4, 6, placed on the magnetic circuit 2, forming an autogenerator together with the operational amplifier 1, and a recording device 5. As a result of reducing the number of windings placed on the magnetic circuit, the number of active and passive elements used and the introduction of new functional connections provides a significant simplification of the device and increases the accuracy of measurements. 2 Il.

Description

1

The invention relates to electrical measuring equipment and can be used for contactless measurement of direct current.

The purpose of the invention is to simplify the device and improve measurement accuracy by reducing the number of windings active and passive by Elec T.- At the same time, the presence of positive feedback between the primary 4 and secondary 6 windings ensures that the output voltage of the amplifier 1 remains unchanged until the total magnetic the flux $, + Ф5 does not reach the saturation flux of the magnetic circuit 2. After k

In order to form JQ total magnetic flux Φ, the oscillator of the oscillator of both the oscillator and the active element are common for both half-oscillations of the oscillator.

Figure 1 presents the block diagram of the device; 2, temporary di jogs, which explain the operation of the device.

The device for measuring direct current (Fig, 1) is a symmetrical push-pull oscillator with a transformer reverse

20

there is no fs value, the voltage on the secondary winding 6 will change its polarity, which will lead to a change in the polarity of the voltage at the input of amplifier 1, and due to the presence of the same positive feedback, the voltage U at the output of the amplifier will also almost instantly change its polarity and will reach the maximum negative value. This process is periodically repeated, as a result of which, at the output of the amplifier, a variable voltage U of a rectangular form (FIG. 2 a) is formed,

connection, made on the differential amplifier 1. The windings of the oscillator are placed on the magnetic core 2, covering the conductor 3 with a controlled current IK. The primary windings 4 of the autogenerator are connected to the common bus of the device by the first terminal, and the second output through the recording device 5 of the magnetoelectric system is connected to the output of the amplifier 1, the secondary winding of the 6 autogenerator, which serves to create a positive feedback, is connected to the common bus of the device, and the second output - with the input of the amplifier 1.

The device works as follows.

When applied at the time of supply voltage, the output of amplifier 1 is the voltage of one of the polarities. Due to the presence of positive feedback, this voltage U at the output of amplifier 1 almost instantly reaches its maximum value (Fig. 2a).

Under the influence of this (positive) voltage U in the primary winding 4 of the autogenerator, an increasing current i occurs (which creates an increasing magnetic flux flux F, −g in the magnetic circuit 2; -1 where Rw

magnetic resistance of the magnetic circuit 2; Wn is the number of turns of the primary winding 4. This flow in the magnetic circuit 2 is summed with the magnetic flux Phi produced by the controlled current T.- At the same time, the positive feedback between the primary 4 and the secondary 6 windings ensures that the output voltage of the amplifier 1 remains unchanged, until the total magnetic flux $, + F5 reaches the value of the saturation flux of the magnetic circuit 2. After

Q total magnetic flux F reached-

j

0

five

there is no fs value, the voltage on the secondary winding 6 will change its polarity, which will change the polarity of the voltage at the input of amplifier 1, and due to the same positive feedback, the voltage U at the output of the amplifier will also almost instantly change its field rness will reach the maximum negative value. This process is periodically repeated, as a result of which a variable voltage U of rectangular shape (FIG. 2 a) is formed at the output of the amplifier,

The magnetic flux created by the current of the primary winding 4 in the magnetic conductor 2 is approximately triangular in shape and in the absence of magnetic flux 4. generated by the controlled current () is symmetrical about the time axis and changes from - to F5 (Fig 2 b ), In this case, the constant component in the current of the primary winding 4 is missing. If there is a controlled current I in the magnetic circuit 2, a magnetic flux Fp is created that is different from zero, therefore the magnetic conductor 2 is saturated in one direction at a value of Ф5-40 n and in the OTHER direction at a value. Thus, the magnetic flux ft is shifted by , i.e., it becomes asymmetrical with respect to the time axis, a constant of 0 appears in it

35

45

scha f,

 - Phi (figure 2).

With this in

0

five

the current flowing through the primary winding 4 of the oscillator is constant in terms of the current, proportional to the flow FC, i.e. 1, (Fig. 2 g), which is measured by a recording device 5 of the magnetoelectric system.

The device significantly reduces the number of windings placed on the magnetic core, by eliminating the transistors and the limiter amplifier, minimizes the number of active and passive elements, which makes it possible to achieve a significant simplification of the proposed device in comparison with the known one. In the known device, the duration T, and Gg (Fig. 2a) of the half-oscillations of the oscillator depends both on the magnitude of the monitored current and on the resistance in the power supply circuit of the oscillator, including the resistance of the ballast resistor, the resistance of the collector windings and the transistors of the autogenerator themselves, which vary with a change in temperature, in the device due to the use of one common active element of a differential amplifier, one primary and one secondary winding for forming a Formula Formula in the autogenerator of the invention. A device for measuring direct current, comprising a magnetic core encompassing a current-controlled conductor, two windings placed on the magnetic core, a registering device and a differential amplifier, the input of which is connected to the beginning of one winding, the end of which is connected to the common bus of the device, characterized in , in order to simplify and improve the measurement accuracy of both half-oscillations of the oscillator with the exception of ballast-2o nor the output of the differential amplifying resistor, the output signal - n via the recording device soe- roystva, representing an average of the current output amplifier is essentially independent of izmedinen with the beginning of another winding, whose end is connected to a common bus device.

active resistance in the chain of the oscillator, which improves the measurement accuracy of the controlled direct current in comparison with the known device.

Claims (1)

DETAILED DESCRIPTION OF THE INVENTION A device for measuring direct current, comprising a magnetic core, covering a conductor with a controlled current, two windings placed on a magnetic circuit, a recording device and a differential amplifier, the input of which is connected to the beginning of one winding, the end of which is connected to the common bus of the device, that, in order to simplify and improve the measurement accuracy, the output of the differential amplifier through the recording device neither the output of the differential amplifier through the registering device Dinen with the beginning of another winding, the end of which is connected to the common bus device.