Device for geoelectromagnetic

 

(57) Abstract:

The invention relates to a device for frequency soundings, magnetic and electrical excitation of the electromagnetic field. Field of application - out phase-sensitive measurements used in the study of apparent resistivity of the upper layer of the earth in a wide range of frequencies. Effect: increase the measuring accuracy of the real and imaginary components of the electromagnetic field. The device contains the exciter field, the first, second and third control bus, connected respectively to the control inputs of the first and second frequency synthesizers and digital phase shifter, installed between the output of the second frequency synthesizer and control input out phase-sensitive rectifier, connected to the signal input to the sensor field, and the output to the input of a bandpass filter connected to the output signal out phase-sensitive input analog-to-digital Converter connected to the input of the display unit, a power amplifier connected to the output of the first frequency synthesizer connected to the output of the first generator, a second generator connected to the input of the second frequency synthesizer. In the device the LEM power. The first frequency divider connected between the output of the first frequency synthesizer and the control input of the switch, and the second frequency divider between the output of the second frequency synthesizer and control input out phase-sensitive analog-to-digital Converter. The first and second control bus are connected respectively to control inputs of the first and second frequency dividers. Installation input of the second frequency divider is connected to the adjusting input of the second frequency synthesizer and a fourth control bus. 1 Il.

The invention relates to a device for frequency soundings, magnetic and electrical excitation of the electromagnetic field. Field of application - out phase-sensitive measurements used in the study of apparent resistivity of the upper layer of the earth in a wide range of frequencies.

A device for electro method of induced polarization [1] , consisting of inverter (generator), admissions and supply lines, selective amplifier, detector and pulse voltmeter (measuring device). The generator generates bipolar pulses, filled with pulsating voltage. These bipolar pulses in becauseerful highlights from the input voltage signal with a frequency of filling polarizing current pulse.

This signal is detected in the detector and is used for switching the sensitivity of the measuring device that measures at certain times of the input voltage. The known device has the main advantage that the measuring device can operate in standalone mode at a large distance from the generator (generator unit).

However, the known device has the disadvantage consists in the fact that the synchronization of the measuring device relative to the current in the power line is up to a phase, i.e. not determined by the sign of the gradient of the potential bandwidth and induced polarization.

It is known device [2] for electrical exploration method of a charge consisting of a commercially available type station earth-67 and portable digital voltmeter PVC-1. The known device allows gradient (out phase-sensitive measurements at subsonic frequencies over large study areas. However, this device inherent significant disadvantage in lowering the measurement accuracy with increasing operating frequency and at higher sensitivity due to stray radiation elektromagnitnogo field working cha is sensing [3], containing generating device consisting of a first oscillator, power amplifier, the supply of the dipole frequency synthesizer includes a frequency divider and a control circuit, receiving device, consisting of serially connected unit filters, broadband amplifier, detector with the Registrar and connected in series calibration generator, the calibration of the voltage divider and the signal receiver. This device is taken as a prototype. The device prototype improved the accuracy of the measurements by comparing the measured signal with a reference voltage. However, this device has the disadvantage consists in the fact that it is not possible to make out phase-sensitive measurements, and with increasing frequency of the useful signal and the sensitivity significantly decreases the accuracy of the measurements due to parasitic radiation of the electromagnetic field of the operating frequency (MIC effect).

The purpose of the present invention is the improved accuracy of the measurements of the real and imaginary components of the electromagnetic field.

This objective is achieved in that the device for Geoelectromagnetic containing vosmogo and second frequency synthesizers and digital phase shifter, installed between the output of the second frequency synthesizer and control input out phase-sensitive rectifier, connected to the signal input to the sensor field, and the output to the input of a bandpass filter connected to the output signal out phase-sensitive input analog-to-digital Converter connected to the input of the display unit, a power amplifier connected to the output of the first frequency synthesizer connected to the output of the first generator, a second generator connected to the input of the second frequency synthesizer, inputs of the first and second frequency dividers, a switch installed between the exciter field power amplifier the first frequency divider connected between the output of the first frequency synthesizer and the control input of the switch, and the second frequency divider between the output of the second frequency synthesizer and control input out phase-sensitive analog-to-digital Converter, while the first and second control bus are connected respectively to control inputs of the first and second frequency divider, and the installation input of the second frequency divider is connected to the adjusting input of the second frequency synthesizer and a fourth control bus.

In the drawing, and the pout of the frequency synthesizer 2, the power amplifier 3, a switch 4, the exciter field 5, the first frequency divider 6, the first control bus 7, the field sensor 8, out phase-sensitive rectifier 9, out phase-sensitive analog-to-digital Converter 11, the display unit 12, the digital phase shifter 13, the second generator 14, a second frequency synthesizer 15, the second frequency divider 16, the second control bus 17, a third control bus 18, the fourth control bus 19, the transmission line 20, which represents either a two-wire line or radio channel is not included in the unit as a main unit.

The first frequency synthesizer 2 is installed between the output of the first generator 1 and the power amplifier 3 and the first frequency divider 6, the switch 4 is installed between the output of the amplifier 3 and the exciter field 5. The control input of switch 4 is connected to the output of the first frequency divider 6. Out phase-sensitive rectifier 9 is connected by a signal input to the field sensor 8, and the output is through a band-pass filter 10 to the signal input out phase-sensitive analog-to-digital Converter 11. The second frequency synthesizer 15 is installed between the output of the second generator 14 and the inputs of the digital phase shifter 13 and the second frequency divider 16, connected vyhoda Digital phase shifter 13 output connected to the control input out phase-sensitive rectifier 9. The first control bus 7 is connected to the control input of the first frequency synthesizer 2 and the first frequency divider 6, the second control bus 17 to the control input of the second frequency synthesizer 15 and the second frequency divider 16, the third control bus 18 to the control input of the digital phase shifter 13, and the fourth control bus 19 to the set inputs of the second frequency synthesizer 15 and the second frequency divider 16.

The device operates as follows. The first generator 1 produces rectangular pulses with a repetition frequency f0. These pulses arrive at the input of the first frequency synthesizer 2. To the control input of the first frequency synthesizer 2 served as the control code Nywith the first control bus 7. The first frequency synthesizer 2 generates a sinusoidal voltage UC1= Um1sin(0/N0t) = Um1sin0t, where Um1- amplitude,0= 2f0N0is an integer defined by the code Ny,0=0/N0.

The output voltage UC1applied to the inputs of the amplifier 3 and the first frequency divider 6. The first frequency divider 6 generates a rectangular signal Un1= UgSign sin(0/N0Ng)t = UgSign sinnt, where - astate low-frequency signal, Ng- the division ratio set by the code Nyfrom conditions 0n= const.

The output voltage of the first frequency divider 6 is supplied to the control input of switch 4, performing the change of the connection polarity of the exciter field 5 to the output of the amplifier 3. As the actuator field 5 may be used or magnetic dipole (magnetic stimulation), or the supply line AB (electrical stimulation).

Let us dwell on the only magnetic dipole. As a result, in the magnetic dipole flows alternating current Ib= ImSign sinntsin0t, a magnetic moment generated by the dipole is determined in terms of Mg = IbS = MmSign sinntsin0t, where Mm= ImS - amplitude, S is the effective area of the magnetic dipole.

At the point of observation (measurement) of the magnetic field is determined by the expression B = BxmSign sinntsin(0t+ab)+Bnmsin(0t+an), where Bxm- amplitude proportional to the amplitude of the magnetic moment Mm,b- phase shift of the magnetic field relative to the current in the magnetic dipole, Bnm,nrespectively the amplitude and the phase synchronous In the measuring point, tension where Sg- the effective area of the sensor 8,g- phase shift introduced by the sensor 8. The output voltage of the sensor 8 is supplied to signal input out phase-sensitive rectifier 9.

The second generator 14 generates rectangular pulses with a repetition rate of0. These pulses arrive at the input of the second frequency synthesizer 15. The second frequency synthesizer 15 generates a sinusoidal voltage Uc2= Um2sin(0/N0t+ac2) = Um2sin(0t+ac2), where Um2- amplitude,0=0/N0,c2- the initial phase, N0is an integer defined by the code Nyreceived at a control input from the second control bus 17. The output voltage of the second frequency synthesizer 15 is fed to the inputs of the digital phase shifter 13 and the second frequency divider 16. In the digital phase shifter 13 is a shift of the voltage Uc2phase value (C+), whereC- compensating phase shift, the initial phase of 0 or /2.

The output of the low-frequency signal UBout phase-sensitive rectifier 9 is determined by the expression:

< / BR>
where Uxm= (-KB0BxmSg)/2 is the amplitude of the useful signal, KBnminterference.

Installation pulses on the wire 20 on the installation log, the second frequency synthesizer 15 is set in a condition in whichc2= 0, and code control input to the control input of the digital phase shifter 13, set C= -g. Then the output voltage out phase-sensitive rectifier is determined by the expression:

UB= Uxmsin(b+)Sign sinnt+Unbsin(n+).

The output signal UBout phase-sensitive rectifier 9 is fed to the input of bandpass filter 10, in which the frequency selection of the useful signal with a frequency ofnand further out phase-sensitive input ADC 11, to the control input of which a reference voltage Uo= UomSign sinnt from the second frequency divider 16. The ADC 11 converts the analog signal into a digital equivalent of N determined from the expression:

N = SKfUxmsin(b+) = K0Bxmsin(n+)

where K0the product of the coefficients of transmission blocks 8-11, S - slope (coefficient) of the ADC 11, Kf- gain bandpass filter.

From expressions DLH">

When = 0 output code NJm= KoBxmsinbproportional to the imaginary component of the useful signal, and when = /2 output code NRe= KoBxmcosbproportional to the real component of the magnetic field. Output code NJm Reis displayed in the display unit 12.

The proposed device operates similarly in the measurement of electrical signals with the reception grounded line, used as field sensor 8.

From the expressions for NReand NJmit is seen that the output code does not depend on the magnitude of the interference of the operating frequency induced in the sensor field 8 blocks of the device due to microphonic effect, thereby improving the accuracy at higher frequencies0the useful signal, while also improving the sensitivity, i.e. when measuring small signal values.

The proposed device was used as a basis for the development of out phase-sensitive equipment PC 1 manufactured for experiments on the subject, supported by the Fund for basic research (project N 96-05-64252).

Device for Geoelectromagnetic containing the exciter field, the first, second and third control bus, connected respectively to the inputs of upravlyatora frequencies, and the control input out phase-sensitive rectifier, connected signal input to the sensor field, and the output to the input of a bandpass filter connected to the output signal out phase-sensitive input analog-to-digital Converter connected to the input of the display unit, a power amplifier connected to the output of the first frequency synthesizer connected to the input of the first generator, a second generator connected to the input of the second frequency synthesizer, characterized in that it introduced additional first and second frequency dividers, a switch installed between the exciter field power amplifier, and the first frequency divider connected between the input of the first frequency synthesizer and the control input of the switch, and the second frequency divider between the output of the second frequency synthesizer and control input out phase-sensitive analog-to-digital Converter, while the first and second control bus are connected respectively to control inputs of the first and second frequency dividers, and adjusting the input of the second frequency divider is connected to the adjusting input of the second frequency synthesizer and a fourth control bus.

 

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FIELD: geophysical prospecting by electric means by the method of induced polarization.

SUBSTANCE: the device has an exciting field forming unit and a signal measurement unit. The exciting field forming unit has a ship generator, switch forming bipolar DC square pulses, generating plant and a ballast device. The signal measurement unit has a receiving multi-electrode line, resistivimeter, multi-channel measuring device, ship echo sounder, Global Position System receiving indicator and a signal processor. According to the claimed method, the research of the geological medium along the observation outline is carried out by excitation of periodic alternating current pulses and determination of geoelectric medium parameters, geoelectric sections are constructed, a conclusion is made on the presence of a deposit of hydrocarbons according to the exposed anomalies of conduction and the parameters of induced polarization.

EFFECT: enhanced reliability of the research results.

8 cl, 5 dwg

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