SU1387676A1 - Device for measuring magnetic flux - Google Patents

Abstract

The invention can be used in geoelectromagnetic. The purpose of the invention is to test the accuracy of measuring magnetic flux. The device contains a 1 V. high frequency generator, a modulator 2, a high frequency amplifier 3, an amplitude detector 4, synchronous detectors 5 and 11, an integrator 6, blocks 9 and 10 of the reference signal, a narrowband low frequency filter 12 and a cryostat 15 placed in it a superconducting quantum interference sensor 7 with a single josephson junction and a resonant circuit 8. To achieve this goal, a noise detector 13 was inserted, the control unit 14 and new functional connections were formed, 3 sig.

Description

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The invention relates to a device for magnetic measurements and can be used: in geoelectromagnetic exploration,

The aim of the invention is to improve the accuracy of the measurement of the magnetic flux.

Figo 1 shows the structural electrical circuit of the devices proposed in Fig. 2 is a diagram of the control unit in Fig. 3, which are diagrams illustrating the operation of the device where a is the current-voltage characteristic of the device (dependence of the voltage amplitude Up on the resonant circuit on the LEVEL of the current if, high frequency generator) —the device characteristic corresponding to the curve а shzgnova (the dependence of the effective noise voltage U at the output of the noise detector on the current level if), в is the shape of the current envelope ip during four different levels of this TOKaJ g The corresponding changes in the amplitude of the effective noise voltage Ujflj and the dependence of the output signal of the narrow-band low-pass filter (LPF) on the current level if,,

A device for measuring the magnetic flux (see FIG. 1) contains a successively connected high-frequency generator | Torus 1 modulator 2 high frequency amplifier 3 amplitude detector 4 first synchronous detector 5 and integrator 6 whose output is connected to the output of the modulator a 2 ,, Superconducting quantum interferential sensor 7 with a single Josephson junction, inductively coupled to a resonant circuit Sj connected to the output of the modulator 2, the first block 9 of the reference signal S whose first output is connected to the output of the modulator 2s and the second in output - with the second input of the first synchronous detector 5, as well as serially connected second block tO of the reference signal second synchronous detector I and narrowband low pass filter 12J with the second output of the second block 10 of the reference signal connected to the first input of the modulator 2, the second input of the synchronous detector 11 noise detector 13 is connected to the integrator 6 output, and narrowband low-pass filter 12 output is connected via a control unit 14 to the second input of the modulator 2, superconducting quantum interference sensor 7 with one Josephson junction and Nance circuit 8 is placed in a cryostat 15 with liquid helium.

The control unit 14 (see, Fig. 2) consists of a driver 16 for the pulses of the end of the current control, trigger 17 (auto-generator 18, counter-decoder 19, and digital-analogue converter 20.

The device works as follows.

Before starting measurements include

power supply of all nodes. From the output of the control unit 14, a slowly increasing Ugp signal with a UPP signal and an output voltage Uf is applied to the modulator 2.

The first block 10 of the reference signal to the corresponding inputs of the modulator 2 begins to increase the amplitude-modulated current, if (see Fig. 3c). In this case, the UM modulation waveform can

be harmonic or logical (square wave), and the modulation depth is chosen such that the current envelope span ir is 15 ... 20% of the absolute length of the first flat section of the IVC

(see Fig. 3, a and b).

The modulation of the current i leads to an increase in the effective voltage U of noise (u at the output of the detector 13 is a variable noise component of the shape and frequency of the signal 11. If the carrier current ir corresponds to the upstream sections of the noise characteristic (see Fig., 3,6), the signals Osch and UM are in-phase, if the current ip corresponds to the drop-down areas, the noise characteristics

, tics signals U, and UM are antiphase.

The signal Osh is fed to the input of the second synchronous detector 11, controlled by the voltage U of the first output of the second block 10 of the reference signal,

As a result of processing the voltage Urt by a synchronous detector 11 and narrowband low pass filter 12, a signal appears at the output of the latter, which controls the control unit 14 and is quadrature

  - | - U "-4 dt -)

where T is the period of the signal C,,

Taking into account the above considerations of the waveform, it is easy to show that with a small

with the first flat VLH span of the current envelope 1 and when the frequency ratio of the signals of the first and second outputs of the second block of the reference signal is equal to an odd number, the quadrature signal is a derivative of U (j) over a time-varying time carrier current i,, This is absolute, and therefore, the accuracy in the determination of ifzz will be the greater, the greater the number of intense harmonics of the signal Uu) will contribute to the overall quadrature signal. Since the intensity of the harmonics of the voltage Uiu decreases with an increase in their sequence number, it is necessary to take into account the lower ones, starting from the first. From expression (1) it immediately follows that for this the frequency of the signals U and Uui must be the same.

As can be seen from FIG. The voltage ifc is unambiguously related to the sign of the angular coefficient of the characteristic (see Fig. 3.6), and at the minimum point of the noise of the device, it changes from negative to positive.

At the first such inversion of the voltage symbol Csrntz in the control unit 1A, a pulse is generated and the control is terminated and the voltage Usp is fixed at the output of the control unit 14, As a result, the current control process if stops. The value of current ip corresponds to the optimal operating mode of the device.

Claims (1)

Invention Formula A device for measuring the Marfmr flux, which contains a series-connected high-frequency generator, a modulator, a high-frequency amplifier, an amplitude detector, the first synchronous detector and an emitter, whose output is combined with the modulator output, a superconducting quantum ipterference sensor with one The Josephso1 a9 junction inductively coupled to a resonant circuit connected to the output of the motor of the torus, the first block of the reference signal, the first output of which is connected to the output of the modulator, and the second output is connected to the second in One first synchronous detector, as well as a second reference signal unit, a second sigcchronous detector, and a narrow signal low-pass filter in series, the second output of the second reference signal block being connected to the first modulator input, in order to vary the measurement accuracy , a noise detector and a control unit are entered into it; the liar detector input is connected to the integrator's output, and the code is connected to the second input of the second synchronous detector, the output of the control unit is connected to the second input the modulator, and the input to the output of the narrow-band low-pass filter, while the frequencies of the signals from the first and second signals of the second block of the reference signal are equal to each other. CQ3ff {1Z H & KLG / 9ugueg / ro & amp tfff Krgyu / Zprm f fs MSff7eifl f f.i li i & is iLJiJ -Ji “B ir F1 / 13 ) SH