SU1716465A1 - Device for geophysical electrical surveying - Google Patents

Abstract

The invention relates to the field of geophysics, in particular, to devices for measuring the relative phase difference of spectral components in the method of induced polarization on an alternating current. The purpose of the invention is the expansion of functional capabilities while simultaneously reducing the laboriousness of measurements and increasing informativity. The device measures the potential phase difference of the spectral components of single pulses of arbitrary nature and shape and produces a statistical analysis of large arrays of phase parameter values due to the presence of a pulse extraction unit. computing unit and recorder. 3 il.

Description

(/

WITH

The invention relates to geophysics, in particular, to devices for measuring: the relative-relative phase difference of the spectral-1O1 in the method of induced polarization by alternating current.

A device for geo-electric and reconnaissance is known, which contains a field exciting field generator, usually in the form of a rectangular shape, closed "a; grounded AB line. reception grounding line MN, input wideband V (% switch, notch filter, harmonic separation unit. detector and recorder. The device measures the frequency-4 polarization effect. A disadvantage of the known device is the generator group, the need for a new AB line, and low noise immunity, due to the presence of broadband amplifiers, strongly susceptible to intermodulation distortion m.

A device that implements a phase variant of measurements of induced polarization is known. The device comprises an excitation generator loaded onto a grounded AB line, a receiving grounded MN line, a preamplifier, a unit of narrow-band measuring measuring amplifiers tuned; on the frequency of the first and third harmonic of the exciting current, a block of pulse converters, separating the harmonic transition points through zero, a measuring unit that measures the difference of the phases between the first and third harmonic signals through their zero crossing points and converts this difference into digital form, and a stand-alone calibrator connected to the preamplifier. The device operates in dual frequency mode.

About Оv About SL

determines the phase angle p & n, related to the frequency of the first harmonic. The operation of the known device is as follows. The signal from the excitation generator, passing through the medium under study, is distorted, since the various spectral components of the signal pulses acquire a different phase shift. The distorted signal is recorded by the receiving grounded 10 MN line, amplified by the preamplifier, then two spectral components are extracted from the signal using narrow-axis measuring amplifiers, for example, the first and third harmonics, which are simultaneously fed into the pulsed transducer block (first and third harmonic signals in the time interval measured by the measuring unit.

The magnitude of the phase difference at the point of measurement determines the polarizability of the medium under study.

A disadvantage of the known device is limited functional capabilities, namely the need to use an excitation generator with a periodic signal, the information content of the measurements is small, since at one measurement point only one average value is determined (fan, regardless of the complexity of the section being studied.

The aim of the invention is to enhance the functionality while simultaneously changing the complexity of the changes and increasing the information content.

FIG. 1 shows a diagram of the device; Fig. 2 is a variation of a pulse separation unit circuit; FIG. 3 shows diagrams of operation of the pulse extraction unit.

The device (Fig. 1) contains a receiving line MN galvanically connected with the medium under investigation, a second pre-amp 45 amplifier 2, a pulse extraction unit 3, a first pre-amplifier 4, a block of narrow-band measurement amplifiers 5 tuned to the first and third spectral components of decomposition - 50 pulse to the Fourier integral, the first and second keys 6 and 7, the pulse converter 8, the measuring unit 9, which converts the phase difference into a pulse code, the computing unit 10 and 55 the recorder 11, as microcomputers, for example Electronics DZ-28 with a display unit, an autonomous calibrator 12, at the output of which it is possible to form a continuous pulse sequence, as well as single rectangular pulses.

The device works as follows.

The signal from the receiving line MN-1 in the form of single pulses — in the case of operation from artificial pulsed sources — or in the form of a continuous random stream of pulses — in the case of using signals from natural electromagnetic fields (EEMF) —ams to the second preamplifier 2, then to the selection unit pulses 3, which ensures that pulses are received at the input of the first preamplifier 4 with an interval not less than the measurement time of the instantaneous phase difference of the spectral components of the pulse. Isolated and amplified by the first pre-amplifier 4, a single pulse is fed to the input of the block of narrow-band measuring amplifiers 5.

After a single pulse is applied to the input of a block of narrowband measuring amplifiers 5, free oscillations occur at its outputs with selected frequencies o) and 3d) and corresponding phases that pass through keys 6 and 7, which are opened along a given front of a single impulse by the control command pulse selection 3, to the inputs of the pulse converter 8, in which the transition points of the damped sinusoids are taken using comparators. In this case, the pulse extraction unit 3 ensures that the next pulse arrives at the inputs of the measuring narrow-band amplifiers 5 not earlier than the time for the free oscillation of the previous pulse, i.e. zero initial conditions are realized in these resonant systems. Thus, a measurement of the phase difference of the first and third harmonics of each pulse, and not the average phase difference, as in the prototype, is achieved. Using the time of the pulse modulator included in the pulse converter 8, the value of the phase difference is converted into a burst of pulses, the number of which n corresponds to the instantaneous phase difference of the spectral components of a single pulse. Further, this number of pulses. N is fed to the input of the measuring unit 9, in which it is converted into a serial code. compatible with the format of the computing unit 10, which is used by the microcomputer, and depending on the problem being solved, the generated code is fed directly to the register 11 or is grouped into a data array that is stored in the RAM of the computing unit 10. The latter measurement mode is used if EEMF is used as an excitation generator, the initial phase of the spectral components of which (prior to passing through the test medium) is unknown and a statistical processing.

Thus, in order to obtain information on the phase parameter of the EP in the proposed device, it is sufficient to pass a single pulse through the medium under investigation, unlike the prototype, where it is necessary for the generator to obtain similar information, continuous operation of the generator.

If the EMPP is used as a source, the pause between pulses is random and it may happen that the oscillatory process in the block of narrow-band resonant amplifiers 5 does not have time to fade before the next pulse arrives, the instantaneous values of the phase difference of adjacent pulses will be correlated, i.e . distortion of information. To eliminate distortion in the device, there is a pulse extraction unit 3, one of the possible variants of which is shown in FIG. The variant of the block contains the first control switch 13, the broadband amplifier 14, the first and second comparators 15 and 16, the adder -17 OR-NOT, the first differentiating circuit 18, the delay block 19, made, for example, on the Schmidt trigger, the executive trigger 20 , the first output of which is connected to the control input of the key 13, the second output is connected to the keys 6 and 7 (Fig. 1), i.e., it gives a signal Ex. Further, the block contains the element HE 21, the second controlled key 22, the second differentiating chain 23, the second element NOT 24 and the third differentiating chain. 25

The pulse extraction unit operates as follows.

To the input of the pulse extraction unit, pulses of a natural electromagnetic field are received from the second, preamplifier (pos. 26). The comparators 15 and 16 of the positive and negative levels separate the point of zero-crossing pulses (poses 27 and 28), which, having passed through the adder 17 (poses 29), are received through the normally closed second control key 22 and the second differentiating circuit 23 on the input R of the executive trigger 20, which runs on the front

the front of any pulse signal received for the initial.

Executive trigger 20 opens (pos 30) the first control key 13 and transmits a pulse to the input of the block (pos 32). At the end of the pulse action on the falling edge of the output pulse of the adder 17, a delay block 19 is started (pos. 3), which is the leading edge through the third

0 differentiating circuit 25 transfers the executive trigger 2Q, which in turn opens the first key 13, stopping the access of subsequent signal pulses to the input of the block. Simultaneously, the 5 pulse of the delay unit 19 opens the key 22, stopping the transmission of control pulses from the adder 17 to the input R of the executive trigger 20. Since the trigger 20 starts only on the leading edge, in the case of an impulse end of the actuator, the trigger signal does not occur which prevents the transmission of a part of the signal pulse to the output of the pulse elimination unit, i.e. distortion of the initial pulse shape ..

Thus, by adjusting the amount of delay, you can pick up a pause between pulses of a signal of this magnitude, when

0, the quasi-sinusoidal oscillations in the measuring resonant amplifiers 5 (Fig. 1), resulting from the effect of the previous pulse, are completely attenuated, and the device is ready to measure the instantaneous

5, the phase difference of the spectral components of the next pulse.

The introduction of a pulse separation unit makes it possible to measure the instantaneous value of the phase difference between two spectral components of a single pulse transmitted through the medium under study, which allows using single pulses of high power as a generator of excitation pulsed sources.

5 The organization of the pulse extraction unit (Fig. 2) allows the proposed device to function normally with any artificial (continuous, pulsed) or natural source of signals without any alterations, i.e. has advanced functionality.

When used as an excitation generator, the cEMF decreases

5, the laboriousness of the measurements increases the efficiency and environmental compatibility of the proposed device with the medium, while, due to the different amplitudes and paths of the EEMP pulses in the medium, it becomes possible to estimate the vertical section of the medium at the measuring point.

Formula for the device Device: for geoelectrical exploration, containing a series-connected receiving grounded line, the first preamplifier, the block of narrow-band measuring amplifiers, the unit of the pulse converter and the measuring unit, as well as the stand-alone calibrator, and by the fact that. in order to extend the functionality while reducing the complexity of the measurements and increase the information content, between the receiving ground

five

In addition, the second preamplifier and the pulse extraction unit are connected in series with the first line and the first preamplifier, and between the measuring amplifier unit and the pulse converter unit, the first and second switches are connected in parallel, the control inputs of which are connected to the control output of the pulse separation unit, to the output of the measuring amplifier the unit is connected in series with the additionally introduced computing unit and the recorder, and the autonomous calibrator is connected to the second redvaritelnomu amplifier.

.Fi-t. ft. v v. /.

26

lpp

pp

l

.

26

l

27

n

G1P.P28

l

29

P

P

thirty

BUT

32

Fig.Z

V

Claims (1)

A device for geoelectrical exploration, comprising a 5 receiving grounded line, a first preamplifier, a unit of narrow-band measuring amplifiers, a pulse converter unit and a measuring unit, as well as a stand-alone calibrator 10 torch, that, in order to expand the functionality while reducing the complexity of measurements and increasing information content, between the receiving grounded line 15 and the first preamplifier additionally introduced the second preamplifier and the Pulse separation unit are connected separately, and between the measuring amplifier unit and the pulse converter unit, the first and second switches are connected in parallel, the control inputs of which are connected to the control output of the pulse extraction unit, additionally entered computing unit and recorder are connected in series to the output of the measuring unit, and the standalone calibrator is connected to a second preamplifier.