CN108196307B - Technical scheme for sine wave phase induced polarization - Google Patents
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Abstract
“正弦波相位激电的技术方案”是国土资源方面科学方法与应用研究领域的、地质勘探之物探新技术开发，属频率域激发极化法的相位激电分支，测量参数为单频率或多频率的绝对相位和视电阻率。本方案基于窄带滤波可大分贝衰减干扰信号、单频正弦波滤波物理相移可补偿的特性，用单片机锁定正弦波信号，直接刻读相位，在正弦波波峰处模拟采集振幅，具有简单快捷和经济高效的特点，适应各种有色金属的地质普查和详查，并适合强工频干扰和强游散直流干扰的矿山物探。应用该方案解决了目前频谱激电和相位激电的高成本低效益、不适合地质普查、和不适合矿山物探的弊病，可作为现有频率域激电技术应用的快速和便利手段，应用于地质勘探和矿山生产中。
"Technical solution for sine wave phase IP" is the development of new geophysical exploration technology in the field of scientific methods and applications in the field of land and resources, and it belongs to the phase IP branch of the frequency domain excited polarization method. The measurement parameters are single frequency or multiple Absolute phase and apparent resistivity of frequency. Based on the characteristics of narrow-band filtering, which can attenuate interference signals by large decibels, and single-frequency sine wave filtering, which can compensate for physical phase shift, this scheme uses a single-chip microcomputer to lock the sine wave signal, directly engraves the phase, and simulates the acquisition of the amplitude at the peak of the sine wave. Economical and efficient, it is suitable for geological census and detailed investigation of various non-ferrous metals, and is suitable for mine geophysical prospecting with strong power frequency interference and strong wandering DC interference. The application of this solution solves the disadvantages of current spectrum IP and phase IP, which are high cost and low benefit, unsuitable for geological census, and unsuitable for mine geophysical exploration. It can be used as a fast and convenient method for the application of existing frequency domain IP technology. Geological exploration and mine production.
Description
One, the technical field
The invention discloses a technical scheme of sine wave phase induced polarization, belongs to the technical development and application research field of national earth resource science methods, is a novel method for geophysical prospecting technical application in geological exploration, and belongs to a phase induced polarization branch of a frequency domain induced polarization method.
Second, technical background
The technical scheme of sine wave phase induced polarization is called sine wave phase induced polarization for short, and apparent absolute phase psis (mrad) and apparent resistivity rho s (omega m) are measured, so that the method is a novel method independently researched by the inventor and has independent and independent property rights. Frequency domain induced polarization, which comprises two branches of frequency spectrum induced polarization and phase induced polarization, is a new technology gradually popularized in recent years, but the current application is not mature enough, and is only suitable for indoor research and geological detailed investigation and evaluation of other geophysical prospecting anomalies; the sine wave phase induced polarization can solve the defects of high cost and low benefit, unsuitability for geological survey and mine geophysical prospecting of the existing frequency spectrum induced polarization and phase induced polarization, and can be used as a quick and convenient means for the application of the existing frequency domain induced polarization technology in geological exploration and mine production.
Time Domain Induced Polarization (TDIP)
Time domain induced electricity is transmitted and supplied in forward and reverse directions by using pulse square waves with equal intervals, a receiver measures a primary field of the supplied electricity, the resistivity rho s (omega m) is calculated, then a secondary electric field induced on a geologic body is measured at the moment when the primary field disappears, and normalization processing is carried out on the amplitude of the relative primary field to obtain the time domain induced electricityThe method comprises the steps of (1) excitation parameters η S (%), (A, B) electrodes for power supply and emission of signals with the pulse width of 10S (second) and the period of 40S in early time domain excitation, and (△ U) reception by a receiver due to the influences of a ground electric field, a natural potential SP and the likeMNThe signal needs manual compensation during operation, so that the operation of the instrument for single-point measurement takes 1 minute at the fastest speed, the instrument with the power supply pulse width selectable to be 2S/4S/8S and the period 8S/16S/32S appears in the later period, the receiver performs manual compensation and automatic compensation, and the field measurement speed is correspondingly accelerated.
Time domain induced polarization provides a large amount of induced polarization anomalies for geological exploration, and the time domain induced polarization is effective in mineral exploration of nonferrous metals, but a considerable amount of induced polarization anomalies exist due to interference of graphitization (carbonaceous materials are subjected to magma hydrothermal deterioration), and verification fails when the time domain induced polarization is suspected to be sulfide minerals such as copper, lead, zinc and the like, so that the application of the time domain induced polarization is subjected to bottleneck in mineral exploration.
(II) Spectrum Induced Power (SIP)
The principle of frequency spectrum induced polarization is derived from complex resistivity existing in rock and ore strata, according to W.H, Pelton and the like, by measuring a large number of rock and ore samples and outcrops and describing the frequency characteristic of an induced polarization effect by a Kerr-Kerr model, the expression of the complex resistivity is as follows:
where ρ is0Denotes the resistivity at zero frequency, and m, τ, c denote the polarizability (or charging rate), time constant, and frequency-dependent coefficient, respectively.
Theoretically, the frequency Spectrum Induced Polarization (SIP) is 10-3--n102In the wide-area observation of Hz, but in practical application, a signal source can only transmit a limited number of frequency points, represented by the common domestic V-6/V-8 multifunctional induced polarization instrument (Phoenix Canada) and GDP-32 II multifunctional induced polarization instrument (Belleville Corp.) in China, when the spectrum induced polarization works in the field, 18-27 frequency points are generally selected to transmit and receive in a wide frequency band of 0.0313-256 Hz, a receiver processes received signals through a wave trap for power frequency interference signals, then performs signal amplification and A/D acquisition in the wide frequency band according to a transmission square wave logic time sequenceObtaining the zero-frequency resistivity rho s through Fourier transform and DSP operation0And the resistivity rho s, the charging rate (activation rate) ms, the time constant ts and the frequency correlation coefficient cs of each frequency point.
According to the experiment and field practice of frequency spectrum induced polarization, geologically metal sulfide ore and mineralization are high polarization, low resistivity, medium time constant (tau s = 0.1-2 s), small frequency correlation coefficient (cs <0.2), compact ore-rich time constant (tau s = 2-10 s), graphite is low resistance, high excitation, large time constant (tau s > n10s) and large frequency correlation coefficient (cs >0.3), the graphite is used as the basis for geophysical prospecting, good effect is obtained in practice, the method is effective for distinguishing copper, lead, zinc and other ore body anomalies and graphite interference methods, the bottleneck problem of time domain induced polarization is solved, wherein the time constant tau s is related to the size of crystal particles of the ore body, the tau s value is larger when the crystal particles are smaller and more compact, the two-dimensional section with abnormal electrical depth tau s isoline can well correspond to the ore body production shape, the indicating effect is obvious.
The frequency spectrum induced polarization technology is complex, the signal channel of the instrument requires precision and low drift, the signal A/D acquisition requires high precision, and the digital signal processing requires DSP operation, so the equipment cost is high; the signal channel adopts a trap filter to filter power frequency interference, so that not only is the suppression of the power frequency interference incomplete (a V-8 instrument suppresses the attenuation of the power frequency of 50Hz/60Hz to 40dB), but also physical phase shift of similar frequency points can be caused by filtering, so that the measurement error is increased; the frequency point multipurpose duration used for sweep frequency measurement, taking a V-8 instrument sweep frequency of 25 frequency points as an example, one rotation of data automatic acquisition needs 35 minutes, and the single-point measurement is completed by auxiliary work such as electrode running and the like, and the time is 35-60 minutes; the receiver collects extremely low frequency signals, the extremely low frequency signals are influenced by a ground electric field and a natural potential, the requirements of electrode grounding conditions are strict compared with time domain induced polarization and phase induced polarization, and the construction difficulty is extremely high; due to a plurality of factors, the frequency spectrum induced polarization is suitable for indoor research and geological detailed investigation and is not suitable for large-area geophysical prospecting general investigation.
(III) Current State of domestic Current phase induced Electricity
The Kerr theory complex resistivity formula is developed with a real part and an imaginary part, and in an alternating electric field, the real part and the imaginary part exist between the real part and the imaginary partThe phase difference is expressed in the potential difference △ U measured on the geologic body in the field induced geophysical prospectingMNRelatively high emission current IABThe phase lag phi is certain, and when the frequency is constant, the more the induced electrical effect is strong, the larger the delay phase phi is; the geophysical prospecting measures the delay phase of a certain frequency, called the (absolute) phase induced electrical measurement of a certain frequency, and measures the relative difference of phases of different frequencies, called the relative phase difference induced electrical measurement.
At present, the commonly used phase induced polarization in China, such as FX-1 Focus phase instrument, absolute phase measurement, WSJ-3 phase induced polarization instrument and relative phase difference measurement, all of which use the frequency coherence technology, i.e. a constant current source form is used for synchronizing pulse emission source signals, a receiver multiplies current synchronization signals (sine waves) and synchronization orthogonal signals (cosine waves) with measurement signals respectively and then performs integral filtering to obtain complex variable direct current real variables and direct current virtual variables, then the virtual and real components are divided and then inverse tangent is obtained to obtain the phase, and the real virtual variable root mean square is calculated to obtain complex amplitude, wherein the formula is as follows:
the FX-1 Fophase instrument is a typical intermediate stage of time domain induced polarization to frequency domain induced polarization, continuously emits single-frequency rectangular waves (symmetrical square waves) with the frequency less than 0.25Hz, and has the advantages that the time efficiency of measurement is improved because no power failure interval of time domain induced polarization exists, the measurement parameters are the time domain excitation rate η s, the resistivity rho s and the absolute phase psi s of a frequency point of frequency domain induced polarization, and FX-1 is 10-1The measured properties of the excitation rate η s and the phase psi s are equivalent to each other in the measurement of the Hz frequency band, the useful information is not greatly improved, the bottleneck problem which is the same as that of time domain induced electricity is faced, and the method has no substantial significance for distinguishing the sulfide ore abnormity and the graphite interference.
The WSJ-3 phase induced polarization instrument is a new phase induced polarization instrument which is advanced in China at present, and is divided into 9 frequency points within the range of 0.03125-8 Hz, namely { 8Hz,4Hz,2Hz,1Hz,0.5Hz,0.25Hz,0.125Hz, 0.0625Hz,0.03125Hz }, and five groups, wherein each group takes five adjacent frequency points as a group, is combined according to a pseudo-random sequence, and is transmitted in the form of positive and negative constant-current square waves. After filtering the power frequency interference signal, the receiving signal channel performs coherent detection processing on ten paths of broadband signals of five frequency points, wherein each frequency point has respective synchronous and orthogonal two paths of coherent signals, and the phases and amplitudes of the five frequency points are obtained through A/D acquisition, imaginary-real variable division and arc tangent operation. The WSJ phase induced polarization measurement result can distinguish sulfide abnormity from graphite interference by comparing the relative phase difference of a high frequency band with the relative phase difference of a low frequency band, solves the bottleneck problem of time domain induced polarization, and is better applied to field geophysical prospecting; however, as the WSJ exciter and the spectrum exciter are the same, multi-frequency aliasing signals such as extremely low frequency and the like are required to be acquired in a wide frequency band, the main defects of poor electrode grounding condition and high field labor intensity are not improved, and the instrument is required to use integral filtering to eliminate alternating current signals after frequency coherence. Compared with time domain induced polarization, phase induced polarization represented by WJS is still complex in principle, poor in power frequency interference resistance, poor in grounding condition, long in measuring point period, and the field practicability needs to be further improved.
Reference for foreign phase induced polarization instrument
At present, imported instruments are used for measuring phase induced polarization in China, such as V-8 and GDP-32 II multifunctional electrical instruments, and in fact, the instruments are called CR (complex resistivity) or SIP (spectral induced polarization) measurement although the instruments are used for measuring phase induced polarization, because the instruments measure phase induced polarization of psi s or measure rho、The data acquisition mode and the data processing of the spectrum induced polarization of m, tau and c are the same, the spectrum induced polarization or the phase induced polarization is output, only because the output mode of software is different, and no difference exists in equipment cost and engineering cost, for example, a V-8 instrument needs 1 minute for measuring the phase of one frequency point 1Hz at the fastest speed, a plurality of frequency points need to be measured during actual use, the accumulated total consumption time is the same as the spectrum induced polarization, so that the phase induced polarization measurement of geological general survey property is carried out by using an imported type multifunctional electrical method instrument, and the economic cost is very low.
In the last 60 years of the century, phase-excited electrical instruments were first developed in the former Su Union, and "Kazak geophysical instruments" factories developed "Naja 3B L vehicle-mounted base stations which can perform absolute phase measurement of electric field and magnetic field and relative phase measurement of two frequencies, and B L-phi light base stations which can perform relative phase measurement of two frequencies only.
The excitation transmission of the Soviet Union adopts silicon controlled single-frequency pulse square wave transmission, the first harmonic and the third harmonic of the square wave are used in the measurement, no matter the measurement device of a vehicle-mounted base station or a B-L-phi portable receiver (a plug-in portable frequency-selecting oscillator) is provided with two signal channels, two frequency points are filtered and selected simultaneously, one frequency is selected to transmit the fundamental frequency of the square wave and suppress the third harmonic of the square wave, and the other frequency is selected to be the third harmonic and suppress the fundamental frequency. The frequency-selecting resultant signal can be respectively connected with a detector circuit (such as diode rectification and filtering) by a manual switch, and can be displayed and read by an analog pointer meter, so that the frequency-selecting resultant signal can be used for signal monitoring and resistivity calculation.
When measuring the relative phase difference, the soviet union uses an approximate calculation method, under the condition that the cosine value of the fundamental frequency is approximately equal to 1 and the sine value of the fundamental frequency is approximately equal to the frequency chord angle, the relative phase difference of the third harmonic and the first fundamental frequency harmonic is calculated by a special means, two frequency-selecting signals are respectively shaped into square waves, then the time sequences of the edges of the respective square waves are compared with each other, and the relative phase is measured under the condition of a quartz oscillator and pulse analog counting; when measuring the relative phase difference, the synchronous reference does not need to be transmitted. When the vehicle-mounted base station carries out absolute phase measurement, one frequency point is measured each time, and the frequency selection processing of sampling the emission current is carried out at the emission base station aiming at square wave fundamental frequency or third harmonic wave and synchronous logic of wireless emission; when the receiver measures the absolute phase, firstly, the wireless synchronization is led into a receiving channel, the frequency-selecting output is compared with the synchronous signal, the phase base number is measured, then, the measuring point signal is led into the receiving channel, and the absolute phase compensated by the base number is measured.
The phase induced polarization method of Sulian people is based on analog counting of a quartz crystal oscillator and complicated switching of a mechanical manual switch, advanced equipment is made under the electronic technical condition of the year, a great deal of successful practice is carried out in the field, systematic research is carried out on various power supply measuring device methods for transmitting and receiving phase induced polarization, and the phase induced polarization method plays an important role in promoting the development of phase induced polarization in China. The principle of Su Union phase induced electricity is clear, the method is simple, the equipment is heavy, the measurement takes an empirical formula as a guide, a laggard electronic technology is used, and the principle is laggard after the current time domain induced electricity due to the difference of times and is completely not suitable at present; but the method has the characteristics of simplicity, is consistent with the idea of sine wave phase induced polarization, and has important reference function on sine wave phase induced polarization as a result of field practice.
(V) search new conclusions
The technical scheme of sine wave phase excitation is not reported in other documents except that the inventor proposes 'sine wave phase excitation' in a 'geophysical prospecting and chemical prospecting' journal.
The technical scheme of sine wave phase induced polarization comprises a sub scheme of sine wave emission and single-channel phase induced polarization instrument receiving, a sub scheme of symmetrical square wave emission and three-channel sine wave phase induced polarization instrument receiving, and a method of front Soviet Union phase induced polarization, wherein the method is similar to the second sub scheme of the invention and has no intersection with the first sub scheme. The method of the Soviet Union is through the approximate processing of dual signal contrast, the invention is that the frequency of the one-chip computer locks and carves and reads accurately, the former can only process two routes of relative signals, only can get a phase parameter once to measure, the latter can process three routes of signals at the same time, measure and get three absolute phase parameters once; the former has no important characteristic of narrow-band filtering large-decibel attenuation interference signals and also has no concept of 'sine wave phase induced polarization', and the latter systematically provides a measurement mode of sine wave phase induced polarization by an advanced mature electronic technology, takes a single-frequency sine wave as a main characteristic, and particularly has an obvious characteristic of a first sub scheme of sine wave transmitting and receiving; the technical scheme of sine wave phase induced polarization is an improved and perfect measure aiming at the frequency domain induced polarization application in China at present, and is invented in the aspects of quick measurement and convenient application, belongs to new technology development, and is very obvious in technical difference with the former Soviet Union.
Third, the invention of the patent
According to the current situation of frequency spectrum excitation and phase excitation, the technical scheme of sine wave phase excitation solves the problems that: the method has the advantages that the measurement principle is simplified, the equipment cost is reduced, the labor intensity of geophysical prospecting is reduced, the production efficiency is improved, the phase spectrum change rule of phase induced polarization is mined, more geophysical prospecting information is obtained with the minimum investment, the application range of the phase induced polarization is expanded, and the potential economic benefits of scheme application are increased.
At present, the defects of frequency spectrum induced electricity and phase induced electricity are many, but the contradictory focus is mainly reflected in 'measurement of extremely low frequency signals', because of extremely low frequency, ① a large amount of interference signals cannot be eliminated (including earth electric field, natural potential, industrial scattered direct current interference, uneven electrode excitation and the like), ② grounding conditions are poor, deep excavation and brine pouring are needed for arranging electrodes, the labor intensity is high, the ③ instrument has long operation and measurement period, ④ requires precise and low drift of the instrument, and the cost is high.
According to previous researches, the complex resistivity rho is reduced along with the increase of the frequency f of an alternating electric field, the delay phase phi approaches to zero at low frequency and high frequency, the tau value and the c value are different along with the different shapes of different plastid crystal particles on the logarithmic coordinate of the frequency, the frequency fc corresponding to the peak value psi max of the delay phase is different, and the phase value changes to be in a normal distribution on the two sides of the peak value; according to the test statistics of ore samples, the fc of loose and infected pyrite is more than 10Hz, the fc range of the vein or lump infected sulfide ore body is between 1Hz and 10Hz, the fc of the lump sulfide ore body is about 1Hz, the fc of the compact lump sulfide ore body is about 0.5Hz, and the frequency of the graphite phase peak value fc is less than 10-2Hz, in the frequency band available for excitation, the phase of the graphite always decreases with increasing frequency, when the frequency is 10-1Near Hz, the phase size of graphite and other metal sulfide ore bodies is not greatly different, and when the frequency is more than or equal to 1Hz, the phase of graphite is obviously reduced. Therefore, depending on the target of prospecting, the fieldThe external actual geophysical prospecting can have pertinence, the frequency point of phase induced polarization measurement can work near fc of a corresponding target geologic body, the measurement of other frequency points can be greatly reduced on site, particularly, the frequency point measurement of extremely low frequency is avoided, the working efficiency can be improved, the instrument cost can be reduced, the grounding condition of electrodes is reduced, the labor intensity of field work is reduced, and the breakthrough direction of the defects of the existing frequency spectrum induced polarization and the existing phase induced polarization is improved.
According to theoretical calculation and experiments of the university of the south-middle industry, see the attached drawings, wherein fig. 2 is a theoretical calculation spectrum curve of a certain sulfide ore, fig. 3 is a theoretical calculation spectrum curve of graphite, fig. 4 is a test spectrum curve of a certain pyrite sulfide, fig. 5 is a test spectrum curve of graphite, in a frequency band below 32Hz, the absolute value of the metal sulfide ore body excitation spectrum delay phase increases along with the increase of frequency, the absolute value of the graphite delay phase decreases along with the increase of frequency, and when the frequency is about 0.1Hz, the two are approximately equal, and when the frequency is more than 10Hz, the contrast is huge; in the conventional time domain excitation, the pulse square waves with equal intervals are used for forward and reverse power supply, the widths are respectively 2S, 4S and 10S, the amplitude of fundamental frequencies in the square waves accounts for the main body, the fundamental frequencies are about 0.1Hz, the result of geophysical prospecting cannot effectively distinguish sulfide ore bodies from graphite carbonaceous non-ore bodies, and the result is also consistent with that shown in figures 2, 3, 4 and 5.
Therefore, under the condition of avoiding graphite interference and reducing the labor intensity of field geophysical prospecting, the phase-excited measurement frequency range is preferably between 1Hz and 50Hz, and the lower the frequency is, the higher the amplitude of the measurement signal is, the higher the signal-to-noise ratio is, but the lower the field working efficiency is; the higher the frequency, the greater the electromagnetic interference in the measurement. The technical scheme of sine wave phase induced polarization selects a frequency range of 1Hz to 12.5Hz, meets the theoretical requirement and accords with the field geophysical prospecting practice. Although the phase induced polarization selection frequency tends to predict fc of the target, the phase induced polarization selection frequency is not necessarily fc, and is comprehensively determined according to the ore finding target, the geological environment and the working efficiency; the frequency is low, so that the method is suitable for searching massive metal sulfides, but the working efficiency is reduced and the labor intensity is increased due to the low frequency, the frequency is a little high, and the method is suitable for searching infective sulfides and precious metals such as gold and silver associated with pyrite; according to the distribution rule of the induced polarization phase spectrum, the method can realize the geophysical prospecting effect approaching the frequency spectrum induced polarization by measuring the phases of more than three frequency points close to the target fc and calculating fc and psi max indoors by a mathematical means in a mode of least workload and most labor saving.
At present, a simple and reliable absolute phase induced polarization measuring instrument is not available in China, besides the complex principle of the traditional coherent technology, a key problem is actually that broadband measurement is adopted, the contradiction problem that 50Hz power frequency interference is reduced and physical signal phase shift caused by filtering is avoided is not solved and well processed, and in order to safely reduce the power frequency interference, the phase induced polarization can only work in a lower frequency range. The core of sine wave phase excitation is that a signal acquisition channel recognizes a single-frequency sine wave, a narrow-band filtering technology is adopted, other useless signals can be attenuated in a large decibel mode, single-frequency signals are fixed and can be compensated and eliminated, and under the condition that the parameters of a filtering channel are fixed and unchanged, the physical phase shift generated in the channel is also fixed and can be compensated and eliminated.
The main content of the invention is shown in figure 1, wherein the current signal I in the AB power supply loop is influenced by the influence of the earth inductive load between the AB electrodes, the inductance of the power supply long lead and the change of the grounding condition of A, B electrodesABAnd a supply voltage signal VABWith a phase delay phi therebetweenABPotential difference △ U of measuring point MNMNAnd a supply current IABThe induced phase psi s between the two phases is locked by a singlechipAB△ U relocked based on the synchronization signalMNThe signal parameter psi s can be directly read on the single chip microcomputer by a time counter, and the signal amplitude can be positioned at the sine wave crest of the locking frequency signal for A/D acquisition. The sine wave phase excitation is not the DSP operation of the broadband Fourier transform and is not the synchronous phaseThe amplitude acquisition of the dry detection plus the arctangent operation is not the root mean square operation of real and imaginary variables, so the method belongs to a simple and direct principle scheme.
The scheme design of sine wave phase induced polarization signal transmitting and receiving is divided into two sub schemes of sine wave inversion transmitting and single channel receiving and symmetrical square wave transmitting and three channels receiving simultaneously. In order to reduce the cost of transmitting equipment and reduce electromagnetic interference radiation generated by a system, and different from other frequency spectrum excitation and phase excitation, the signal transmission of sine wave phase excitation is transmitted in a mode of a voltage stabilizing source, and the actual transmitting current is synchronous with the signal and is obtained through actual measurement of a transmitter. When sine wave waveform signals are transmitted, no high-frequency signal is generated, when symmetrical square waves are transmitted, the transmitter does not intentionally require that current signals of all harmonics are consistent and synchronous, and the transmitter respectively measures the 1/3/5/triple harmonic current signals synchronously and transmits the signals to the receiver through various channels; because no other energized constant current source is used for pulse emission, voltage spike radiation caused by current abrupt change and electromagnetic interference caused by radiation are obviously reduced when the voltage direction of the pulse is changed.
The sine wave phase induced polarization is characterized in that:
① the receiving signal channel adapts to single-frequency sine wave, because the frequency band is very narrow, the system adopts big decibel filtering attenuation to strong power frequency interference and strong wandering DC interference, the physical phase shift of single-frequency sine wave caused by channel filtering can be compensated, the exciter is not concerned about other frequency passing through the channel, and is not influenced.
② sine wave phase induced polarization instrument, its absolute phase and frequency amplitude are measured directly after the frequency locking of the single chip, simple and fast in principle.
③ sine wave phase induced polarization receiving comprises a single-channel phase induced polarization instrument matched with sine wave transmission and a three-channel sine wave phase induced polarization instrument matched with symmetrical square wave transmission, wherein the former receives single-frequency point or multi-frequency point sine wave signals in series and uses a common signal filtering channel, the latter collects signals of three frequency points in parallel and simultaneously, each frequency point has own signal filtering, and the mode of signal processing of each channel is completely the same as that of the single-channel receiver.
④ sine wave inversion emission, the emitter emits standard sine wave, which can be single frequency continuous emission or multi-frequency combination order circulation emission, when the symmetrical square wave is continuously emitted, it is spread according to the square wave Fourier transform, the emitter synthesizes sine wave emitting fundamental frequency signal 1/3/5 subharmonic wave, which satisfies the three-channel sine wave phase induced polarization instrument can accomplish the absolute phase and amplitude measurement of three frequency points.
⑤ the working frequency of sine wave phase excitation is designed in the range of 1 Hz-12.5 Hz on the basis of analyzing the excitation target, reducing the difficulty of field operation and reducing the cost of equipment, and the time of single-point multi-frequency measurement can be completed within several seconds.
⑥ according to the distribution rule of the induced phase frequency spectrum, the phase psi s of more than three frequency points is measured, fc and psi max are approximately calculated by mathematical means (Gauss normal curve inversion or simple unitary quadratic equation inversion), and the geophysical prospecting effect of approaching the spectrum induced electricity can be realized by using the least workload and the most labor-saving mode.
⑦ sine wave phase induced polarization instrument has strong power frequency interference resistance and wandering direct current interference resistance, is especially suitable for developing mine (district) geophysical prospecting, and can operate in deep tunnel and command mining production on site.
Four, sine wave phase induced polarization implementation principle
Geophysical prospecting signal emission of sine wave phase induced electricity
The sine wave phase induced signal transmission has two forms, one is standard sine wave waveform transmission, can be transmitted continuously at single frequency, and can also be transmitted circularly at multiple frequencies, the available frequency range is 1 Hz-12.5 Hz, each frequency point is transmitted continuously for 3 periods during sequential transmission, for example, 1248 four-frequency sine wave transmission is: 1Hz,1Hz,1Hz,2Hz,2Hz,2Hz,4Hz,4Hz, 8Hz,8Hz,8Hz,1Hz,1Hz.. The other is continuous emission of symmetrical square wave with fixed frequency, and the fundamental frequency of the square wave is 1 Hz-2.5 Hz.
An excitation transmitter for sine wave waveform emission is shown in a schematic block diagram in fig. 6, wherein a front-stage switching power supply and a rear-stage switching power supply of a transmitter set are provided, a front stage is an input-output high-frequency transformer isolation boosting type and controls the amplitude of output voltage of sine waves, the rear-stage switching power supply is responsible for inversion of the sine wave waveforms and is in a four-tube bridge type, switching tubes { S1, S1 ' } are switched simultaneously, { S2, S2 ' } are switched simultaneously, the duty ratio of the switching is changed as shown in fig. 7, in the sine wave inversion, the switching tubes { S1, S1 ' } and { S2, S2 ' } are switched alternately, when the angle is 0-180 degrees, { S1, S1 ' } are switched { S2, S2 ' } is switched, the tubes are integrated with reverse diodes, freewheeling is realized at 180 degrees to 360 degrees, and freewheeling is realized by { S2, S2 ' } is switched on { S1, S1 ' } is switched off, { S1, and S1 ' }. The output of the rear-stage switching power supply is filtered by two-stage LC filtering to filter the high-frequency switching signal of the switching power supply and change the high-frequency switching signal into a low-frequency sine wave.
The transmitter inverts the sine wave, and the waveform correction is completed by the control of the single chip microcomputer. The inverted sine wave output is subjected to voltage division sampling by a non-inductive resistor, is isolated from an ISO122 operational amplifier and then is connected with an A/D signal input end of a single chip microcomputer, the single chip microcomputer is compared with a standard sine wave signal after data acquisition, and the duty ratio of the inverted output of the rear-stage switching power supply is changed and controlled at any time according to a comparison result so as to achieve and keep the integrity and the indeformable of the output sine wave signal.
The transmitter outputs the synchronous signal of current, adopts the current sampling of a shunt meter, and after the synchronous signal is changed into a small signal in the shape of sine wave voltage by an isolation operational amplifier, on one hand, the output is driven by a large-current operational amplifier and is output to a synchronous small cable, on the other hand, square wave logic pulse of emission current is obtained through zero comparison, the pulse is transmitted to the wireless transmission synchronization, transmitted to the absolute value converter of the current signal and also transmitted to the singlechip, and the amplitude of the transmitted current signal is collected by controlling A/D through the singlechip, according to the measured current, comparing with the output current set by the system, the output voltage of the front-stage switch power supply is feedback controlled and adjusted in real time, the current output by inversion is kept stable, meanwhile, the single chip microcomputer continuously corrects the GPS time service through the zero-crossing pulse, adjusts the initial phase of the output sine wave, and ensures that the output current synchronization is consistent with the GPS time service in real time.
The principle block diagram of the symmetrical square wave transmitting excitation transmitter is shown in figure 8, and because the transmitter generally has high power which can reach dozens of kilowatts and outputs more than +/-1000V of voltage, the front-stage switching power supply can adopt two switching power supplies of general commercial products with 0-600V direct current voltage stabilization output to be connected in series from the aspects of system heat dissipation, convenient maintenance and cost reduction, and the output voltage of the front-stage switching power supply is controlled by a binary 12-bit PWM signal output by a single chip microcomputer. The back stage of symmetrical square wave output is general IGBT full bridge phase inversion with the switching frequency of 1 Hz-2.5 Hz and is controlled by a single chip.
The wireless synchronization or GPS synchronization of the symmetrical square wave induced emission corresponds to the pulse voltage signal output by the transmitter synchronously; and the output of the small cable is a current synchronization signal output by the transmitter output current signal shunt meter measurement and the isolation operational amplifier drive.
Signal receiving of sine wave phase induced electricity
A, receive single channel sine wave phase induced polarization appearance receiver of sine wave transmitting signal:
the core of the single-channel sine wave phase excitation receiver is a high-speed low-power consumption 16-bit or 32-bit single chip microcomputer, such as a dsPIC30Fxxxx series, an STM32F103xx series and the like, and is required to have I2The working frequency of sine wave phase excitation can be manually input by a keyboard, and can also be actually measured according to the transmission frequency during measurement synchronization, the parameters measured by a receiver are apparent resistivity rho s (omega M) and absolute phase psi s (mrad), the input impedance of the MN interface is 10M omega, △ U, and the likeMNThe range of received signals is +/-0.01 mV-2000 mV (peak value), wherein the maximum superposed power frequency interference is allowed to exceed +/-1000 mV, the phase measurement range is 0-1500 mrad, and the phase resolution is less than 0.01 mrad.
In order to ensure that the receiver can normally work in various severe environments in the field, the selection type of the temperature indexes of all components of a receiver circuit meets the automobile-level standard, namely the performance of all parameters is not changed when the receiver circuit works at the temperature of-40 to +125 ℃, when the receiver circuit is actually used, the lowest condition of all parameters must meet the temperature requirement of-40 to +85 ℃ in the industrial level, the lowest condition of all parameters comprises all chips, resistors, capacitors, quartz crystals and the like, and used printed boards and soldering tin, the components are subjected to parameter screening and aging treatment before being welded, and all the components are sealed and stored at constant temperature in stock before being welded; this ensures that the operating parameters of the final instrument product are not affected by ambient temperature and thus do not change during use.
The circuit principle of the single-channel phase-excited receiver is shown in figure 9, and a differential signal delta U of a measuring electrode M, NMNWhen accessing the signal lead-in end of the receiver, firstly pass through C0And R0The inlet blocks the DC signal below 1Hz, when it enters the first stage operational amplifier U0A, it has a2 times fixed gain, then it is divided by the linear digital potentiometer RW1, then it enters the second stage fixed gain operational amplifier U0B, the digital potentiometer RW1 is passed through the single chip computer by I2The C bus control, 256-stage change, and the fixed gain operational amplifier form the pre-stage control of the program control automatic gain. The system is divided into a front stage program control gain and a rear stage program control gain, the rear stage program control gain consists of a digital potentiometer RW2 and a fixed gain operational amplifier U4B, the mode is the same as that of the front stage, the purpose is to improve the gain at the front stage as much as possible when the power frequency interference amplitude is small so as to ensure enough signal to noise ratio, if the power frequency interference amplitude is large enough to block a front-stage signal, a U5 comparator judges the signal amplitude, when the power frequency interference amplitude is larger than 3.3V, a pulse signal of a falling edge is provided for a single chip microcomputer CPU, the CPU reduces the front-stage gain step by step according to the signal so that the total signal amplitude amplified by the front stage is smaller than 3.3V, if the total signal amplified by the front stage contains the power frequency interference with higher amplitude, the total attenuation is realized in the following low-pass filtering, and the low-pass filter channel attenuates the frequency above 50Hz by; then the amplitude of the useful signal is reduced and the gain is improved by the program control of the later stage. The single chip microcomputer carries out total automatic gain control according to the A/D conversion result, when the A/D conversion result is larger than 3.8V (Vref =4V), the potentiometer is linearly downshifted, and when the A/D conversion result is smaller than 3.0V, the potentiometer is linearly upshifted. Through the processThe signal of controlling gain and low-pass filtering output, through stopping direct zero calibration and precise operational amplifier A2 drive, then with electronic switch SWA, and with passing the zero comparator A3 at a high speed, the sine wave signal that the phase induced polarization instrument measures, through the zero cross comparison, output and sine wave 0-180 degrees of corresponding high level square wave, the square wave is the zero level when the sine wave is 180 degrees-360 degrees, this square wave is connected with input interface that the pulse signal of CPU catches directly, then the rising edge and accurate time of the falling edge of the square wave pulse will be caught by CPU; meanwhile, the zero-crossing comparator outputs the inverted level of the square wave to control the SWA electronic switch, and the alternating current sine wave output by the A2 is converted into a unidirectional direct current signal by taking an absolute value in combination with a differential input precision operational amplifier A5, and then is sent to an A/D input interface of the single chip microcomputer.
The receiver first captures the AB-powered transmission synchronization before the receiver measures normally. When the receiver works in a capture and transmission synchronization mode, a synchronous sine wave signal is converted into a symmetrical square wave signal through a filter and a zero crossing comparator, the symmetrical square wave signal is accessed to an external interrupt interface of a CPU, the CPU collects the rising and falling time of a pulse level, calculates the frequency and the transmission time of the actually transmitted sine wave, keeps the sine wave clock synchronization (frequency locking) with AB transmission by modifying the cycle number of an on-chip timer, and the cycle number is a 32-bit binary system, the number unit of the cycle number is a single chip microcomputer instruction cycle, generally can reach dozens of MHz of high frequency, so the resolution ratio of the phase of the sine wave is very high. Because the singlechip clock is a high-temperature-resistant quartz crystal oscillator, the stability and the accuracy are high, and as long as the clock of AB power supply is not changed, the phase shift psi of AB current is ensuredABThe stability is unchanged, and as long as the singlechip is not powered off, the singlechip and the transmission signal of the AB are stably kept synchronous locking.
After the singlechip captures the locking synchronization, when the receiver is switched into general geophysical prospecting measurement, the receiver is adjusted to a normal measurement mode through a keyboard. In the measurement mode, signals accessed by MN are filtered and pass through a zero comparator at high speed, on one hand, the signals are accessed to the outside of a CPU in a square wave mode for interruption, and the CPU reads out an excitation phase by capturing the count value of a timer synchronously locked with AB transmission; at the same timeAccording to the captured phase time, ¼ emission period is delayed, and when the sine wave signal changes from 0 degree to 90 degrees, the A/D sampling of the single chip microcomputer is turned on to obtain delta UMNThe positive peak voltage of the signal delays the emission period of the microspheres according to the captured phase time until the sine wave signal changes to 270 degrees, and then the A/D sampling of the singlechip is turned on to obtain the delta UMNAnd the negative peak voltage of the signal is multiplied by the coefficient of the geophysical prospecting device after the average value of the positive peak value and the negative peak value of the A/D sampling is obtained, and then the multiplied value is divided by the AB emission power supply current to obtain the apparent resistivity of the current measuring point. Because the A/D acquisition is positioned at the wave crest of the sine wave, the signal amplitude is large, the average filtering after the absolute value conversion of the alternating current signal is not needed, the resistivity acquisition is not delayed, and the signal-to-noise ratio is high and the speed is high. See fig. 10, 11.
The signal filtering channel of the single-channel receiver and the frequency attenuation curve chart of circuit simulation are shown in figure 12, the signal gain is-0.4 dB to +2.4dB in the range of 1Hz to 12.5Hz, the frequency attenuation above 50Hz of power frequency is greater than-147.4 dB, and the low-frequency signal attenuation less than 0.1Hz is greater than-79.4 dB; because of the filtering relation, the waveform of the measuring signal lags behind, the simulation physical phase shift curve is shown in figure 13, because the receiver circuit adopts the components and parts which resist the temperature change, after aging treatment, various parameters of the filter circuit can not change along with the change of the environmental temperature, and the physical phase shift is also fixed at fixed frequency; the signal of the filtering channel of the sine wave phase induced polarization instrument is only sine wave with fixed frequency, and the transmitting synchronous signal obtained by synchronous measurement and small cable synchronization and the same-frequency signal measured at each measuring point are both passed through a common filtering channel, the physical phase shift of the signals is the same, and the signals are automatically compensated and offset on the singlechip; therefore, the channel filtering does not influence the measurement result of the measuring point excitation phase, which is the characteristic of the sine wave phase excitation receiver.
B, receiving a three-channel sine wave phase induced polarization instrument receiver of a symmetrical square wave transmitting signal:
the frequency of the symmetrical square wave emission is 1 Hz-2.5 Hz, such as 1.5Hz/2Hz, the Fourier series expansion is carried out, sine waves of multiple harmonic waves such as fundamental frequency 1.5Hz/2Hz, triple frequency 4.5Hz/6Hz, quintuple frequency 7.5H/10Hz, heptatuple frequency 10.5H/14Hz, etc. are provided, except that the amplitude of a signal of one, three and five times of frequency is large, the amplitude of other high-order harmonic waves is a small part of the output power of the transmitter, and the amplitude can be ignored.
The three-channel sine wave phase induced polarization instrument collects signals of three frequency points, the signals respectively pass through three special ten-order Butterworth narrow-band filtering channels, when a 1.5Hz square wave is received and transmitted, a first channel is designed to filter a passband (-3dB at 0.7Hz) and a stopband (-40dB at1.8Hz), the attenuation of the signals larger than 4.5Hz is larger than-75 dB, the attenuation of the signals smaller than 0.35Hz is larger than-95 dB, and the gain of the signals in the range of 0.9Hz to 2Hz is 1.7dB +/-1 dB; the passband of the second pass filter is (-3dB at 0.7Hz), the stopband is (-45dBat 2.6Hz), the central 4.5Hz signal gain is 3V/V times, the gain in the range of 4.5Hz +/-0.3 Hz is plus 9.0dB to plus 9.6dB, and the attenuation of the signal with the frequency less than 2.8Hz and greater than 7.2Hz is greater than-70 dB; the third channel filters the passband (-3dB at 1Hz), the stopband (-40dB at 2.6Hz), the central 7.5Hz gain is 5V/V times, the attenuation of the signal with the frequency less than 4.5Hz is more than-73.38 dB, the attenuation of the signal with the frequency less than 10Hz is more than-44 dB, and the attenuation of the signal with the frequency more than 12Hz is more than-68 dB. The simulation graphs of the frequency attenuation and the physical phase shift of the three filtering channels are shown in the attached figures 14, 15, 16, 17, 18 and 19, and the overall circuit diagram of the three-channel sine wave phase induced polarization instrument receiver is shown in the attached figure 20.
The three-channel sine wave phase induced polarization instrument is characterized in that three independent signal channels are respectively synchronized, signal filtering is respectively carried out, program-controlled automatic gain is respectively carried out, high-speed zero-crossing comparison of sine wave signals is respectively carried out, phase inversion is respectively carried out by an electronic switch to complete absolute value conversion of alternating current to direct current, A/D conversion is respectively carried out at 90-degree and 270-degree angles of sine waves, and the data acquisition modes of induced polarization phases and amplitudes of three frequency points of the three channels are completely the same as those of a single-channel sine wave phase induced polarization instrument.
(III) sine wave phase induced signal synchronization
The sine wave phase induced polarization receiver has four modes to obtain the synchronous signal of the emission source, and selects the synchronous signals according to the preferred sequence, namely wireless synchronization for receiving wireless emission signals, GPS synchronization for receiving GPS, synchronization for accessing small cables and measurement synchronization, wherein the first two are digital pulse signals which are directly connected with a pulse interface of a singlechip, and the second two are analog signals which are input through an MN port and a system signal filtering channel. The operation of the method is to set the receiver to be in a measurement synchronization mode, and transmit synchronization is obtained through MN electrode grounding measurement at a geophysical background abnormal point common to a strong field source region. The small cable synchronization is a basic synchronization mode of the system, the measurement mode is also in a measurement synchronization mode, but the MN inputs a small cable signal led out from the transmitter end; the small cable signal is a transmitting current waveform signal which is sampled and isolated by a transmitter, the size of the signal is 1V-2V of peak value, and the tail end of the small cable is provided with a matching resistor of 100 omega. The synchronization of the receiver can be updated at any time by the wireless transmission synchronization and the GPS synchronization, for example, the receiver is automatically linked and synchronized in the process of measuring the running pole and the mobile base station, the normal measuring time is not influenced, but the two types of synchronization are performed by using a small cable as a physical phase shift scale before use, the scale value is stored by the power failure of a single chip microcomputer, in the phase excitation measurement, the single chip microcomputer adds the logic time received by the wireless synchronization or the GPS synchronization and the physical phase shift of the scale, and then the logic time sequence is compared with the logic time sequence of sine wave zero-crossing comparison signals with different frequencies of each measuring point, so that the absolute alignment phase with different frequencies of each measuring.
In the phase induced polarization measurement process, if the AB power supply electrode is grounded well, the phase shift psiABAnd after the receiver is stable and unchanged, the transmitter and the receiver keep consistent frequency locking and synchronization through the quartz clock in subsequent measurement as long as the transmitter and the receiver are not shut down, the receiver does not need to find synchronization, and the quartz clock is subjected to factory adjustment and calibration, so that the synchronization error is in an allowable range. If wireless synchronization or GPS synchronization is used, even if signal transmission locally affecting wireless synchronization due to valley topography or the like, or reception of GPS due to sheltering reasons such as dense forest or tunnel or the like, will not be affectedAnd (4) normally carrying out the excitation measurement. In the measurement, if small cable synchronization or wireless transmission synchronization is carried out at each measuring point, the sine wave phase excitation is slightly poor in the grounding condition of the AB electrode, and psiABAnd the normal operation can be realized even under the condition that the phase drift is unstable. If psiABThe phase drift is unstable, and simultaneously, the wireless synchronization, the GPS synchronization and the small cable synchronization are inconvenient to be carried out, so that a certain receiver can be used for monitoring and measuring psi in real time near a transmitterABThe parameter (psi s measurement of small cable signals) can be recorded according to a time axis, and the indoor correction processing can be carried out on the phase parameters collected by other receivers, so that the sine wave phase induced polarization can still be normally carried out.
The small cable synchronization of the three-channel sine wave phase-excited instrument, wireless synchronization and GPS synchronization have the same requirements and operation as those of a single-channel phase-excited instrument. However, the wireless synchronization and GPS synchronization of the symmetrical square wave transmission are the voltage V of the transmitted pulseABSignal synchronization, while wireless synchronization and GPS synchronization of sine wave waveform transmission are currents IABThe signals are synchronous, so the scale data of the wireless synchronization and the GPS synchronization of the three-channel sine wave phase-excited instrument comprises psiABVariable, andABthe grounding of the AB power supply electrodes is different, so that after the grounding of the AB electrodes is changed every time, the three-channel phase excited receiver needs to be scaled again by a small cable to comprehensively correct the three-frequency point phiAB+ physical phase shift, or, under the condition that the existing scale targets of each three-channel receiver are consistent, after the grounding of a new transmitting power supply electrode is changed, carrying out psi measurement of 1/3/5 three frequency points on a new small cable signal by using a certain receiver, and measuring △ psi of three frequency points after the grounding of the AB electrode is changedABThe variation quantity is that all receivers can normally use the existing scale parameters to measure, and finally offset correction is carried out on the acquired psi s parameters; if the number of receivers is surplus, the full-time detection psi can be realized by one receiverABThen other receivers can measure normally without psiABThe effect of drift variation.
Fifthly, sine wave phase induced polarization:
1. the sine wave phase is excited, and the method has the characteristics of simple and quick principle, economical and practical equipment, light instrument and high data sampling speed. Because AB electrode emission frequency is higher, the geophysical prospecting single-point measurement can be accomplished in several seconds, compares other induced polarization appearance, improves the work efficiency more than 10 times at least.
2. The sine wave phase is excited, the emission frequency is more than 1Hz, the graphite carbon interference can be effectively eliminated, and the phase response to the metal sulfide ore body is sensitive.
3. The sine wave phase is excited, the phase acquisition of the receiver is not influenced by channel filtering, and the data acquisition is accurate and reliable.
4. Unlike other frequency spectrum excitations and phase excitations, the signal transmission of sine wave phase excitations is transmitted in a mode of a voltage stabilizing source. The sine wave transmission does not have any high-frequency signal, and the symmetrical square wave transmission does not adopt a constant current source mode adopted by other excitation, so that the voltage spike radiation caused by the sudden change of current and the electromagnetic interference caused by the radiation are obviously reduced when the pulse direction is changed. The sine wave phase is excited, the frequency of a received signal is between 1Hz and 12.5Hz, other signals are not concerned and are not influenced, and the influence of any high-frequency spike pulse radiation can be avoided, so the sine wave phase is not only green and environment-friendly, but also has strong anti-noise and adaptability to electromagnetic interference, can normally work in areas with strong power frequency interference and strong stray direct current interference, and is suitable for mine geophysical prospecting.
5. The sine wave phase induced polarization has a more flexible signal transmitting and receiving synchronization mode than other frequency spectrum induced polarization and phase induced polarization, and the wireless synchronization and GPS synchronization modes are less influenced by the change of external conditions and have strong adaptability to various environments.
6. Sine wave phase excitation is slightly poor in grounding condition of AB transmitting electrode, and psiABThe system can work normally under the condition of unstable phase drift; because the full alternating current signal is adopted, the receiver automatically eliminates the influence of direct current and extremely low frequency unstable factors, the grounding condition of the MN receiving electrode is lower than that of other induced polarization, the field operation speed is high, and the quality is good, so compared with other induced polarization, the sine wave phase induced polarization has stronger adaptability to field geology.
7. The emission principle of the symmetrical square wave excitation is simple, the equipment cost is low, the power is low, and the large-area and large-polar-distance deep geophysical prospecting is convenient to carry out.
Sixth, the present invention foreground
The technical scheme of sine wave phase induced polarization is a new method successfully invented based on the requirement of cheap operation on the basis of summarizing the existing frequency spectrum induced polarization and phase induced polarization, solves the bottleneck problem of time domain induced polarization, overcomes the defects of high cost and low benefit of the frequency spectrum induced polarization and the existing phase induced polarization, has the characteristics of higher measurement speed than the frequency spectrum induced polarization, the existing phase induced polarization and the time domain induced polarization, has the lowest relative requirement on grounding conditions, is simple, quick, economical and efficient, can be used as an important supplement of the application methods of the frequency spectrum induced polarization and the phase induced polarization technology, becomes a quick and convenient means for popularization of the induced polarization technology, and provides mineral exploration service for geological general investigation and detailed investigation.
The sine wave phase induced polarization is particularly suitable for mine (district) geophysical prospecting, and the over-time domain induced polarization and other frequency domain induced polarization in application can become important means used in mineral enterprises such as nonferrous metals and the like in mine production and prospecting. The existing frequency spectrum excitation and phase excitation can only develop ground geophysical prospecting in 'noon break' when the industrial electricity utilization is stopped in a mine (region), while sine wave phase excitation can develop excitation work at any time in the environment of an industrial power grid, rail traffic, a lift elevator and an electromagnetic crane, not only can be used for ground geophysical prospecting, but also can develop underground phase excitation in a deep tunnel where the industrial electricity utilization cannot be stopped, and can indicate an ore storage space on site to guide tunnel production. Therefore, future users of sine wave phase induced power not only have geological schools, land and mine departments for land and earth resource exploration, gold troops, numerous mine nations, enterprises in private enterprises, small mine owners and the like, and have considerable expected economic benefits.
Description of the drawings
FIG. 1: sine wave waveform corresponding absolute phase psi s and main power supply V thereofAB、IABA logical relationship diagram of (1);
FIG. 2: a theoretical calculation spectrum curve of a certain sulfide mineral is extracted from a large master thesis in China and south, namely 'summer training silver, numerical simulation of a multi-frequency induced polarization relative phase method and physical simulation research';
FIG. 3: the theoretical calculation spectrum curve of graphite is extracted from the research of 'summer training silver, multi-frequency induced polarization relative phase method numerical simulation and physical simulation' of the large master thesis in south-central province;
FIG. 4: an experimental spectrum curve of a pyrite sulfide mineral is extracted from the research on numerical simulation and physical simulation of a multi-frequency induced polarization relative phase method in the large master thesis of China and south China;
FIG. 5: the experimental spectrum curve of graphite is extracted from the research on the summer silver training, the numerical simulation of the multi-frequency induced polarization relative phase method and the physical simulation of the large master thesis in the south and the central province;
FIG. 6: the principle sketch of an induced-polarization transmitter for sine wave waveform inversion transmission;
FIG. 7: a sine wave waveform inversion emission post-stage switching power supply duty ratio change diagram;
FIG. 8: the principle sketch of an excitation transmitter for transmitting symmetrical square waves;
FIG. 9: the single-channel sine wave phase induced polarization instrument receiver principle diagram is shown;
FIG. 10: an acquisition schematic diagram of absolute (delay) phase and amplitude of sine wave phase induced polarization;
FIG. 11: an acquisition schematic diagram of absolute (advanced) phase and amplitude of sine wave phase induced polarization;
FIG. 12: a simulation frequency attenuation curve graph of a filtering channel of the single-channel sine wave phase induced polarization instrument;
FIG. 13: a physical phase shift curve graph of the simulation frequency of a filtering channel of the single-channel sine wave phase induced polarization instrument;
FIG. 14: a three-channel sine wave phase induced polarization instrument 1.5Hz narrow-band filtering simulation frequency attenuation curve graph;
FIG. 15: a physical phase shift curve diagram of 1.5Hz narrow-band filtering simulation frequency of the three-channel sine wave phase induced polarization instrument;
FIG. 16: a three-channel sine wave phase induced polarization instrument 4.5Hz narrow-band filtering simulation frequency attenuation curve graph;
FIG. 17: a physical phase shift curve diagram of 4.5Hz narrow-band filtering simulation frequency of the three-channel sine wave phase induced polarization instrument;
FIG. 18: a 7.5Hz narrow-band filtering simulation frequency attenuation curve graph of a three-channel sine wave phase induced polarization instrument;
FIG. 19: a physical phase shift curve diagram of 7.5Hz narrow-band filtering simulation frequency of a three-channel sine wave phase induced polarization instrument;
FIG. 20: the three-channel sine wave phase induced polarization instrument receiver principle diagram.
Claims (1)
1. A sine wave phase excitation method is characterized in that: the transmitter transmits sine wave or symmetrical square wave signals in a constant voltage mode, the system respectively collects transmitting current and receiving voltage in real time, the core technology of the collection mode is embodied in the processing of single-frequency sine wave signals, which is represented in signal narrow-band filtering, and filtering physical phase shift can be compensated, and the filtering physical phase shift can be compensated: under the condition that circuit parameters are not influenced by the environment, in a signal channel of the depth narrow-band filtering, the physical phase shift of a single-frequency sine wave measuring signal generated by the filtering is the same as the physical phase shift of a same-frequency sine wave calibration signal of an emission source and the physical phase shift generated when the signal passes through the same filtering channel of a receiver, the phase difference between the calibration signal and the measuring signal is consistent and unchanged before and after the signal passes through the filtering channel, the phase difference between the calibration signal and the measuring signal is measured by a single chip microcomputer, and the result is not influenced by the physical phase shift generated by the channel depth narrow-band filtering; the single-frequency signal is convenient for the single-chip microcomputer to process after being filtered and shaped;
the method for transmitting and receiving the sine wave phase induced polarization signal comprises a sine wave transmitting and single-channel sine wave phase induced polarization instrument receiving sub-scheme and a symmetrical square wave transmitting and parallel three-channel sine wave phase induced polarization instrument receiving sub-scheme;
the principle of the excited transmitter for transmitting sine wave waveforms is as follows: the front stage is an input and output high-frequency transformer isolation boost type and controls the output voltage amplitude of a sine wave, the rear stage is responsible for inversion of a sine wave waveform and is of a four-tube bridge type, wherein switching tubes { S1, S1 '} are switched simultaneously, { S2, S2' } are switched simultaneously, in sine wave inversion, the switching tubes { S1, S1 '} and { S2, S2' } are switched alternately, at 0-180 degrees, { S1, S1 '} are switched on { S2, S2' } are switched off, { S2, S2 '} tube integrated reverse diodes freewheel, at 180-360 degrees, { S2, S2' } are switched on { S1, S1 '} are switched off, { S1, S1' } tube integrated reverse diode freewheel, the rear stage switching power supply outputs a high-frequency switch LC filtering signal, and the sine wave is filtered by two-stage low-frequency switch;
the transmitter inverts the sine wave, the waveform correction of the sine wave is completed by the control of a single chip microcomputer, the inverted sine wave is output, is subjected to voltage division sampling by a non-inductive resistor, is isolated from an ISO122 operational amplifier and is then connected with an A/D signal input end of the single chip microcomputer, after the data is collected by the single chip microcomputer, the data is compared with a signal of a standard sine wave, and the duty ratio of the inverted output of a rear-stage switching power supply is changed and controlled at any time according to a comparison result so as to achieve and keep the integrity of the output sine wave;
the transmitter outputs the synchronous signal of current, adopts the current sampling of a shunt meter, and after the synchronous signal is changed into a small signal in the shape of sine wave voltage by an isolation operational amplifier, on one hand, the output is driven by a large-current operational amplifier and is output to a synchronous small cable, on the other hand, square wave logic pulse of emission current is obtained through zero comparison, the pulse is transmitted to the wireless transmission synchronization, transmitted to the absolute value converter of the current signal and also transmitted to the singlechip, and the amplitude of the transmitted current signal is collected by controlling A/D through the singlechip, according to the measured current, comparing with the output current set by the system, the output voltage of the front-stage switch power supply is feedback controlled and adjusted in real time, the current output by inversion is kept stable, meanwhile, the single chip microcomputer continuously corrects the GPS time service through the zero-crossing pulse, adjusts the initial phase of the output sine wave, and ensures that the output current synchronization is consistent with the GPS time service in real time;
the principle of the symmetrical square wave transmitting excitation transmitter is as follows: because the transmitter is generally high-power and can reach dozens of kilowatts, and the output is more than the voltage of +/-1000V, the front-stage switching power supply can adopt two switching power supplies of general commercial products with 0-600V direct-current voltage stabilization output to be connected in series from the aspects of system heat dissipation, convenient maintenance and cost reduction, the output voltage of the front-stage switching power supply is controlled by a binary 12-bit PWM signal output by a singlechip, the rear stage of symmetrical square wave output is general IGBT full-bridge phase inversion, and the phase inversion switching frequency is 1 Hz-2.5 Hz and is controlled by the singlechip;
the wireless synchronization or GPS synchronization of the symmetrical square wave induced emission corresponds to the pulse voltage signal output by the transmitter synchronously; the output of the small cable is a current synchronization signal output by the transmitter output current signal shunt meter measurement and the isolation operational amplifier drive;
a single-channel sine wave phase induced polarization receiver is characterized in that a 16-bit or 32-bit single chip microcomputer with high speed and low power consumption is adopted as a core, an I2C/SPI/USART/USB interface is required, the single-channel sine wave phase induced polarization receiver has high-speed wide pulse upper and lower edge positioning capturing capability, the phase time of a zero-crossing comparator can be accurately captured, the capacity of conducting A/D sampling on sine wave crest positioning is achieved, the A/D resolution is not smaller than 12 bits of a binary system, 32/32 or 32/16 hardware division instructions are provided, resistivity and phase parameters of each measuring point under a complex geophysical prospecting device can be calculated in real time, the working frequency of sine wave phase induced polarization can be manually input by a keyboard and can be actually measured according to the transmitting frequency during measurement synchronization, the parameters measured by the receiver are apparent resistivity rho (omega) and absolute phase psi (mrad), and the input impedance of the interface is 10M omega, △ UMNThe range of a received signal is +/-0.01 mV to +/-2000 mV, wherein the maximum superposition power frequency interference is allowed to exceed +/-1000 mV, the phase measurement range is 0 to +/-1500 mrad, and the phase resolution is less than 0.01 mrad;
in order to ensure that the receiver can normally work in various harsh environments in the field, the selection type of the temperature indexes of all components of a receiver circuit meets the automobile-level standard, namely the performance of all parameters is not changed when the receiver circuit works at the temperature of-40 to +125 ℃, when the receiver circuit is actually used, the lowest condition of all parameters must meet the temperature requirement of-40 to +85 ℃ in the industrial level, the receiver circuit comprises all chips, resistors, capacitors, quartz crystals, used printed boards and used soldering tin, the components are subjected to parameter screening and aging treatment before being welded, and all the components are sealed and stored at constant temperature in stock before being welded; thus, the working parameters of the final instrument product can be ensured not to be influenced by the ambient temperature and not to change in use;
the circuit principle of the single-channel phase induced polarization receiver is as follows: differential signal Δ U of measurement electrode M, NMNWhen accessing the signal lead-in end of the receiver, firstly pass through C0And R0The inlet blocks the DC signal below 1Hz, when it enters the first stage operational amplifier U0A, it has a2 times fixed gain, then it is divided by the linear digital potentiometer RW1, then it enters the second stage fixed gain operational amplifier U0B, the digital potentiometer RW1 is passed through the single chip computer by I2The system is divided into a front program-controlled gain part and a rear program-controlled gain part, the rear program-controlled gain part consists of a digital potentiometer RW2 and a fixed gain operational amplifier U4B, the mode is the same as that of the front part, the purpose is to improve the gain at the front part as much as possible when the power frequency interference amplitude is small so as to ensure enough signal-to-noise ratio, but if the power frequency interference amplitude is larger so as to block a front signal, a U5 comparator judges the signal amplitude, when the signal amplitude is larger than 3.3V, a pulse signal of a falling edge is provided for a single chip microcomputer CPU, and the CPU reduces the front gain step by step according to the signal so that the total signal amplitude of the front part amplification is smaller than 3.3V; if the total signal after the pre-stage amplification contains power frequency interference with higher amplitude, the number of the signals is attenuated in the subsequent low-pass filtering, and the low-pass filter channel attenuates the frequency above 50Hz to minus 147 dB; then the amplitude of the useful signal is reduced, and then the gain is raised by the program control of the later stage, the single chip computer makes the total automatic gain control according to the result of A/D conversion, when the A/D conversion result is greater than 3.8V, the potentiometer is linearly downshifted, and when the A/D conversion result is less than 3.0V, the potentiometer is linearly stepped up, the signal output by the program control gain and the low-pass filtering is driven by a stopping zero calibration and precision operational amplifier A2, then is connected with an electronic switch SWA and a high-speed zero-crossing comparator A3, the sine wave signal measured by the phase induced polarization instrument outputs a high-level square wave corresponding to the sine wave of 0-180 degrees after zero-crossing comparison, the square wave is zero level when the sine wave is 180-360 degrees, the square wave is directly connected with an input interface for capturing a pulse signal of the CPU, and then the precise time of the rising edge and the falling edge of the square wave pulse can be captured by the CPU; at the same time, it hasThe zero comparator outputs the inverted level of the square wave to control the SWA electronic switch, combines with the precision operational amplifier A5 with differential input, converts the AC sine wave output by A2 into a unidirectional DC signal by taking the absolute value of the AC sine wave, and then sends the unidirectional DC signal to the A/D input interface of the singlechip;
before the receiver normally measures, the receiver firstly captures the emission synchronization of AB power supply, when the receiver works in a capture emission synchronization mode, the synchronous sine wave signal is changed into a symmetrical square wave signal through a filter and a zero crossing comparator, an external interrupt interface of a CPU is accessed, the CPU collects the rising and falling time of pulse level, the frequency and the emission time of the actually emitted sine wave are calculated, then the CPU keeps synchronizing with the sine wave clock emitted by the AB by modifying the cycle number of an on-chip timer, the cycle number is 32-bit binary, the number unit of the cycle number is the instruction cycle of a single chip microcomputer, and can reach dozens of MHz of high frequency, so the resolution ratio to the sine wave phase is very high, as the single chip microcomputer clock is a high temperature resistant quartz crystal oscillator, the stability and the accuracy are very high, as long as the clock supplied by the AB power is not changed, as long as the phase shift of the AB current is stable and unchanged, as long as the singlechip is not powered off, the singlechip and the transmission signal of the AB are stably kept synchronous locking;
after the singlechip captures locking synchronization, when the receiver is switched into general geophysical prospecting measurement, the receiver is adjusted to a normal measurement mode through a keyboard, in the measurement mode, signals accessed by MN are filtered and pass through a zero-crossing comparator at high speed, on one hand, the signals are accessed to the outside of a CPU in a square wave mode for interruption, and the CPU reads an excitation phase through capturing the count value of a timer synchronously locked with AB transmission; meanwhile, according to the captured phase time, 1/4 emission period is delayed, and when the sine wave signal changes from 0 degree to 90 degrees, the A/D sampling of the single chip microcomputer is turned on to obtain delta UMNThe positive peak voltage of the signal is delayed 3/4 emission period according to the captured phase time, and when the sine wave signal changes to 270 degrees, the A/D sampling of the single chip microcomputer is turned on to obtain delta UMNThe negative peak voltage of the signal is multiplied by the coefficient of the geophysical prospecting device after the average value of the positive peak value and the negative peak value of the A/D sampling is obtained, and then the multiplied value is divided by the AB emission power supply current to obtain the apparent resistivity of the current measuring pointA/D acquisition is positioned at the wave crest of the sine wave, the signal amplitude is large, average filtering after the absolute value of an alternating current signal is converted is not needed, the resistivity acquisition is not delayed, and the signal-to-noise ratio is high and the speed is high;
in a signal filtering channel of a single-channel receiver, the gain of a signal in the range of 1Hz to 12.5Hz is-0.4 dB to +2.4dB, the frequency attenuation of a frequency above 50Hz of a power frequency is more than-147.4 dB, and the attenuation of a low-frequency signal less than 0.1Hz is more than-79.4 dB; because of the filtering relation, the waveform of the measuring signal lags, because the receiver circuit selects the components resisting the temperature change, after aging treatment, each parameter of the filter circuit can not change along with the change of the environmental temperature, so the fixed frequency and the physical phase shift are also fixed; the signal of the filtering channel of the sine wave phase induced polarization instrument is only sine wave with fixed frequency, and the transmitting synchronous signal obtained by synchronous measurement and small cable synchronization and the same-frequency signal measured at each measuring point are both passed through a common filtering channel, the physical phase shift of the signals is the same, and the signals are automatically compensated and offset on the singlechip; therefore, the channel filtering can not influence the measurement result of the measuring point induced polarization phase, which is the characteristic of a sine wave phase induced polarization receiver;
the frequency transmitted by the symmetrical square wave is 1 Hz-2.5 Hz, the Fourier series is expanded, the sine wave of multiple harmonics of fundamental frequency 1.5Hz/2Hz, triple frequency 4.5Hz/6Hz, quintuple frequency 7.5H/10Hz and hepta frequency 10.5H/14Hz is provided, except the amplitude of a signal of one, three and five times frequency, the amplitude of other higher harmonics accounts for a small part of the output power of the transmitter and can be ignored, the three-channel sine wave phase induced polarization instrument measures by using a sine wave signal of one, three and five times frequency transmitted by the transmitter, and the apparent resistivity rho s, the apparent absolute phase psi s and the relative phase difference △ psi s of different frequencies can be obtained at the same time;
the three-channel sine wave phase induced polarization instrument collects signals of three frequency points and respectively passes through three special ten-order Butterworth narrow-band filtering channels;
the three-channel sine wave phase induced polarization instrument is characterized in that three independent signal channels are respectively synchronized, signal filtering is respectively carried out, program-controlled automatic gain is respectively carried out, high-speed zero-crossing comparison of sine wave signals is respectively carried out, phase inversion is respectively carried out by an electronic switch to complete absolute value conversion of alternating current to direct current, A/D conversion is respectively carried out at 90-degree and 270-degree angles of sine waves, and the data acquisition modes of induced polarization phases and amplitudes of three frequency points of the three channels are completely the same as those of a single-channel sine wave phase induced polarization instrument.
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