SU995611A1 - Device for measuring magnetic flux - Google Patents

Abstract

A DEVICE FOR MEASURING A MAGNETIC FLOW, comprising a series-connected high-frequency generator, a modulator, a high-frequency amplifier, an amplitude detector, a first synchronous detector and an integrator, the output of which is connected to the output of the modulator, as well as a superconducting junction with the Josephson junction, The invention relates to devices for magnetic measurements and can be used in geological prospecting. A device for measuring magnetic flux is known, which contains a superconducting circuit with a Josephson junction, connected to a resonant circuit connected via a modulator to a high-frequency generator and to a high-frequency amplifier connected through an amplitude detector to the input of a synchronous detector whose other input is connected to the first output of a low-frequency generator using a synchronous detector inductively coupled to a resonant detector circuit connected to the modulator output, the first block of the reference signal, the first output of which is connected to the modulator output, and the second output with the second input of the synchronous detector, characterized by In order to improve the measurement accuracy, the second reference signal block, the second synchronous detector and the narrowband low-pass filter are additionally entered into it, while the second output of the second block of the reference signal is connected to the first modulator input, the output of the narrowband filter “St. connected to the second input of the modulator, and (L the second input of the second synchronous detector is connected to the output of the amplitude detector, and the ratio of the frequencies of the signals of the first and second outputs of the second block of the reference signal ala selected nechetnymo QO CO ate and connected to the input integrals: torus, whose output is connected to a resonant circuit which is also connected to the output low-frequency generator. However, the known device does not provide high accuracy of measuring the magnetic flux, since the current through the resonant circuit is not stabilized. Of the known devices, the device for measuring the magnetic flux in electrical development is closest to the invention in its technical essence.

Description

The device contains a Josephson junction superconducting circuit inductively coupled to a resonant circuit connected via a modulator to a high frequency generator and to a high frequency amplifier input connected through an amplitude detector to a synchronous detector input, the other input of which is connected to the first generator output low frequency5 and the output of the synchronous detector is connected to the input of the integrator, the output of which is connected to a resonant circuit, to which the second output of the low-frequency generator is also connected

However, since in a known device the current through a resonant circuit is not stabilized 5 it also has a low measuring accuracy.

The purpose of the invention is to improve the measurement accuracy

The goal is achieved by the fact that the device 9 contains a series-connected high-frequency oscillator, a modulator, a high-frequency amplifier TOTiiij amplitude detector, the first synchronous detector and an integrator whose course is connected to the output of the modulator, as well as a superconducting junction with the Josephsine transition inductively coupled to a resonant circuit connected to the modulator output, the first block of the reference signal, the first output of which is connected to the modulator output and the second output; from the second input of the first synchronous detector, The second reference signal unit, the second synchronous detector and the narrowband low frequency filter are additionally inserted; the second output of the second reference signal block is connected to the first modulator input, the narrowband filter output is connected to the second modulator input, and the second input of the second synchronous detector is connected with the output of the amplitude detector, the ratio of the frequencies of the signals of the first and second outputs of the second block of the reference signal is selected odd.

The following is a structural electrical circuit of the device; Fig. 3 shows a graph of the amplitude of the voltage Up on the resonant circuit versus the amplitude of the current (flowing through this circuit; Figures 3-5 are time diagrams of the current amplitude (, bending the voltage Up and voltage V at the output of the amplitude detector for the following cases: a i is equal to the current i Г1, corresponding to the middle of the first flat slope; b) ip if ,,;

c) ip

pi

The device for measuring the magnetic flux contains a superconducting circuit 1 with a Josephson 2 transition, inductively coupled to resonant circuit 3 connected via modulator 4 to a high frequency generator 5 and to the input of high frequency amplifier 6 connected through an amplitude detector 7 to the first synchronous input detector 8, another input of which is connected to the first output of the first block of the reference signal 9, and the output of the first synchronous detector 8 is connected to the input of the integrator 10, the output of which is connected to the resonant circuit 3, to which The second output of the first reference signal block 9 is also connected, the device also contains a second reference signal block I15, the first output of which is connected to the modulator 4, and the second output, whose signal frequency is a multiple and odd relative to the frequency of the first output signal, is connected to the first input of the second synchronous detector 12, the output of which is connected via a narrow-band low-pass filter 13 to the low-frequency input of the modulator 4, and the second input of the second synchronous detector 12 is connected to the output of the amplitude detector 7o d conductive circuit 1 with the transition of the Josephson 2 and resonance circuit 3 are placed in a cryostat 14o

It is known that the dependence of the high-frequency voltage Up on the resonant circuit 3 on the amplitude of the current i p through it is an alternating sequence of steep and gentle sections (Fig2), and the slope of their slopes differs by more than 20 times. With a closed feedback circuit , ie when connecting the output of the integrator 10 to the resonant circuit 3, the position of the sloping portions relative to the axes Up and i remains unchanged when the magnetic flux inside the superconducting circuit I o changes

In the operating mode, the high frequency generator current 5 must be equal to the current 1 1p corresponding to the middle of the first flat section (phY). This correspondence is achieved as follows. The second block of the reference signal 1I produces two signals U sin & t and and sin pcot (n - any integer odd number), which respectively arrive at modulator 4 and second synchro detector 12, modulator 4 modulates the current ip in amplitude with the frequency CO I and the amplitude of its modulation corresponds to the middle of the first flat section (figo3) Voltage at the resonant Circuit 3 Up (figoA) is amplified by a high frequency amplifier 6 and fed to the input of an amplitude detector 7o. Voltage and from its output is fed to the input of a second synchronous detector 12, which multiplies it with voltage and sin PSO to When ij, equal to ip, ( FIG. 5a), the voltage and, coincides in shape with the modulating one, and when a detuning of the current occurs (figo5b and 5c), the voltage of the odd harmonics of the frequency CO appears in its spectrum, which leads to the appearance of a constant voltage at the output of the second synchronous detector 12, for example The third harmonic of frequency 63 in the spectrum of the signal U is the greatest, then the number n in the signal U sin n (0t of the second block of the reference signal 11 should be chosen equal to D0 Dp so that the output of the device does not produce an interfering signal associated with the modulation J frequency ) is selected 50-100 times lower than the frequency of the first block 9 of the reference signal. Thus, the voltage Ug and its sign are unambiguously related to the magnitude and sign of the current detuning 1 f, o Pass the narrowband low-pass filter 13 and go to the modulator 4 in such a phase that feedback is a negative voltage and umenshaetvelichinu detuning and thereby increases the stability of the current i in the resonant circuit 3, and improves the accuracy of the measurement signal {with prolonged period of 100 s or more) magnetic flux is 5 times or more depending on the time izmereniyo

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Claims (1)

A DEVICE FOR MEASURING A MAGNETIC FLOW, containing a series-connected high-frequency generator, a modulator, a high-frequency amplifier, an amplitude detector, the first synchronous detector and an integrator, the output of which is connected to the output of the modulator, as well as a superconducting circuit with a Josephson junction,