SU1673998A1 - Ac/dc sensor - Google Patents

Abstract

The invention relates to electrical engineering and can be used for the transmission of galvanically developed signals proportional to direct or alternating current in various protection systems, regulation, control, in particular, in regulated automated direct and alternating current electric drives. The purpose of the invention is to improve the measurement accuracy in a wide range of current without increasing the power consumption - achieved using integrator 5, differential amplifier 11 and resistors 10, 12 and 13. The sensor also contains transformer 1, differential amplifier 2, resistor 3, transformer 4, resistors 6, 7, differential amplifier 8, resistor 9, output terminal 14, input terminals 15, 16. 2 Il.

Description

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Isobro-nnir refers to an anti-tech and can not use Ran for transmitting galvanically developed signals to a proportional gun or variable control systems, in particular, to control automated electric drives constantly and variablely. current Purpose of the invention improvement of measurement accuracy in a wide range of measurement of an eye 6f uvg / name of consumption

Fig. 1 shows a block diagram of a constant and alternating current sensor in Fig. 2; time diagrams of its operation.

The sensor (FIG.) Contains a transformer 1 which is connected to a secondary winding, a differential amplifier 2 and through a resistor 3 to its non-inversion and an end connected to the beginning of the secondary winding of a transformer 4 by a rotary input of the differential amplifier 2 to the inputs of the integrator 5 a resistor 6 is connected to a common bus to which resistor 1 is also connected to a non-inverting input differential amplifier 2 the end of the secondary winding of the transformer -1 is connected to an inverting differential amplifier 8 and through The resistor 9 is connected to its output / or through a resistor 10 is connected to the inverting input of the differential terminal 11 through a resistor 12 connected to the integrator 5 You can connect the differential amplifier 11 through a resistor T1 to its inverting input and also to with you.) ,, nyl. clamp 14 The beginning of the primary winding of the tra formator 1 and the end of the primary oDMom of the wastes of the formator 1 of the jointed pipes All of the or / taeno are connected respectively to the visible clamps 15 and 16

The anti-venting inputs of the differential reinforce 8 and 11 are connected to a common shield and

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When tpgvii and (measured (or koptroliruemsg 1 hl in the primary winding transformed () s 1 and 4 voltage at the output of the output Ltc, the gene is set up. At the same time, the generator o6pd3i4 riHh L and differential differential amplifier 2 secondary obg och-gch4 to the wound of the formator v L d) mi b and working in auto f IT n mode i} nor 2 a) and on re s.k if chk i i h i (v h g rne

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when the current 6 of the transformer 1 is connected to the current of the transformer 1, the value of which after saturation of the transformer magnetic core reaches the value of Pore, and the voltage on the resistor 6 of the Vnop value (fig. 26) determined by resistors 3 and 7, after which the polarity of the applied voltage is switched to the secondary winding of the transformer 1 from the output of the differential amplifier 2

For this variable component of the voltage formed on the resistor 6, the secondary winding of the transformer 4 is a great resistance because its magnetic circuit is unsaturated and the voltage at the output of the differential amplifier 8 at zero constant component will contain pulsations (Fig 2c) with a frequency equal to the frequency switching the oscillator and the amplitude determined by the value of the voltage Vnop, the parameters of the secondary winding of the transformer 4 and resistor 9

The variable component of the resistor 6 (FIG. 26) simultaneously arrives at the input of the integrator 5 at the output of which a voltage is formed with pulsations in form similar to the pulsations at the output of the differential amplifier 8 (fig. 2d) but having opposite phase and different in amplitude Pulsating signals from the outputs of the differential amplifier 8 and the integrator 5 through resistors 10 and 12, respectively, are fed to the inverting input of the differential amplifier 11 Resistances of resistors 10 and 12 as well as reverse resistor 13 The signals are selected so that the pulsating signals at the inverting input of the differential amplifier 11 mutually compensate each other. At the same time, the output signal of the differential amplifier 11 and therefore the signal at the output terminal 14 of the device will not have pulsations with a frequency corresponding to the oscillator frequency on the differential amplifier 2 (Fig 2e)

When DC or AC current flows through the primary windings of transformers 1 and 4, a constant or alternating voltage appears which is proportional to the voltage across the secondary windings of the transformer 4 and the resistor 9 causes a differential the voltage amplifier 8 of the component of the measured current, which also contains pulsations with the frequency of the oscillator of the oscillator (Fig. 2c)

Similar pulsations, but in opposite phase, are removed from the output of integrator 5 (Fig. 2d).

Thus, at the output of the differential amplifier 11 and, accordingly, at the output terminal 14, a voltage appears that is proportional to the measured current, but does not contain pulsations with the oscillation frequency of the oscillator (Fig. 2e).

Since the active resistance of the secondary windings of transformers 1 and 4 in practical circuits is very small (Ohm fraction), the additional bias caused by the voltage drop on these resistances practically does not reflect on the operation of the circuit and does not change the symmetric mode of self-oscillations of the generator, not dependent from the output voltage of the differential amplifier 8 and the magnitude of the measured current. In the case of precision current measurement to compensate for this bias, differential amplifier 8 is advisable to cover additional positive feedback through a large-scale converter.

Claims (1)

Invention Formula A DC and AC sensor containing two transformers with the same transformation ratios, the primary windings of which, like the secondary windings, are connected in series according to each other, two differential amplifiers, the output of the first of which is connected to the first output of the secondary winding of the first transformer and through the first resistor is connected to its non-inverting input, which through the second resistor is connected to the common bus of the device, the inverting input of the first differential amplifier is connected to the common leads of the secondary windings, and through the third resistor to the common bus of the device, the second output of the secondary winding of the second transformer is connected to the inverting input of the second differential amplifier, which is connected via the fourth resistor with the release of the second a differential amplifier; the outputs of the primary windings of the transformers are input terminals of the sensor, characterized in that, in order to improve the measurement accuracy, a third a differential amplifier, an integrator, and three additional resistors, the integrator input connected to the common leads of the transformer secondary windings, and the output through the fifth resistor connected to the inverting input of the third differential amplifier, which through the sixth resistor is connected to its output and output terminal of the sensor, and through the seventh resistor - to the output of the second a differential amplifier, the non-inverting inputs of the second and third differential amplifiers are connected to a common bus. Fig 2