SU912062A3 - Device for measuring induced polarization - Google Patents

Description

It is also known an EP device for electrical prospecting, in which a system of (a plurality of) potential electrodes connected to a signal meter 2, is used to increase research productivity. Measurement accuracy with this device is low. A proposed device for measuring induced polarization, in which the input current arriving on earth with a known frequency, amplitude and duration is measured as an induced potential on a plurality of consecutive potential electrodes. Each electrical signal goes to the input of the differential amplifier circuit and through it to the device for processing and recording electrical signals. In a more limited aspect, the differential amplifier circuit measures the potential difference between each successively spaced pair of electrodes, then each of these differential measurements refers to an input current pulse having predetermined characteristics of frequency, amplitude, and duration. The output data is obtained in any of several parameters that come to digital stitching, multi-channel recording on a magnetic tape and (or) compiled or digitally constructed graphic form. The proposed device is suitable for use in the pulse and frequency variants of the EP method and provides greater measurement accuracy by increasing the signal-to-ohm ratio and, moreover, the possibility of multichannel information processing, which allows observations to be made at high speed and, therefore, costs i.e. increases productivity and reliability of information. The purpose of the invention is to improve measurement accuracy. In order to achieve this goal, a device for measuring induced polarization containing current electrodes connected to a signal generator, a set of potential electrodes to which a measuring device and recorder are connected by means of a multicore cable, a measuring device made in the form of a multichannel differential amplifier, inputs which are connected to the outputs of the multicore cable and the signal resolution unit, the input of which is directly connected to the output of a multitude of differential differential power. tel, and the exit - from the entrance. the registrar. FIG. 1 shows the layout of the electrodes; in fig. 2 is a block diagram of the proposed device; in fig. 3 is a diagram of the proposed compound; Fig. 4 is a block diagram of a digital averaging circuit; in fig; 5 is a block diagram of another type of system. As shown in FIG. 1, at points 1-12 at some distance, there is a truck 13 and associated equipment placed along the observation line on the surface of the earth, lying above the studied half-space 15. The truck can be any mobile field vehicle in which everything necessary is installed electronic equipment for measurement of induced, polarization parameters. The electromagnetic field is excited in the ground by current electrodes 16 and 17, connected via cables 18 and 19 with equipment in the truck. The receiving cable 20 connects a truck with a plurality of electrodes 21 located at some distance from each other and in contact with the earth's surface. The receiving cable is a ten cable made up of a plurality of pieces of cables 22 connected in series through a series of contacts 23. Then the length of the cable 24 provides a multi-channel connection between the truck and the first contact. Each of the potential electrodes includes a single conductor cable 25, which is also intended to be connected to a suitable contact. These contacts are arranged so as to facilitate quick connection and disconnection and allow the truck to move quickly along the line of observation, as will be described in more detail below. During work on the profile, the current electrodes 16 and 17 excite an alternating current of a given shape, i.e. of a predetermined frequency, amplitude and duration, and measured between successively located potential electrodes 21 located along the receiving cable 20. Thus, the first voltage difference EI is obtained from the voltages measured between positions 4 and 5, the voltage difference E is measured between positions 4 and 5, the difference in voltage EZ is obtained between positions 5 and 6, and so on up to the end potential electrode 21 of those used. The present equipment uses six channels and, therefore, in FIG. 1, only voltages between positions 3 to 9 are taken. The diagram shown in FIG. 1 below the ground surface 15, is the conventional (idealized) image method. data caused by polarization. The data obtained: specific resistance p, frequency effect in percent (SE) or the metal factor value for a given current dipole and a given potential dipole are depicted with the intersection of the lines with a 45 ° slope passing through the midpoints of the two dipoles. Thus, the six values of the measured data (resistivity, SE, or metal factor) that are obtained for a given current dipole and the first potential voltage dipoles are depicted on line 26 with a slope of 45 °, which goes from the positions of current dipole 1 and 2. After measurement gap truck 13 Teets Move to the next position, and the difference voltage EI -Eg will snimats SEQ tion chain dipoles located IU dy numerals 4-10. The data obtained at this next position is deleted on the dotted line 27, parallel to line 26 and shifted relative to it by. one position along the line of observation. By observing the general conditions of the spatial distribution of the marginal field, each dipole can be considered as a whole number of spaces between positions. Thus, all measurements for item 1 are depicted but the second horizontal line 28, all measurements for item 2 are depicted along the second horizontal line 29, and so on for items 3, 4, 5 and 6, measurements are depicted respectively by the EUT: horizontal lines 30-33. The greater the separation between the current and potential dipoles, the more deeply the underlying object is studied. It is important to note that the relationship between the magnitude levels and the actual physical depth is non-linear. In addition, this relationship is determined by geology. In other words, although the value of 6 6 clearly corresponds to an object lying at a greater depth than the value of n 3, it is not necessary that the first depth is twice the second, as could be inferred from the graph in FIG. 1. Another important factor is that as the distances between current and potential dipoles increase and the volume of space covered by the measurement increases, both in width and horizontally. Thus, the pseudoglobin plot only indicates large relative positions of the anomalous object, and additional interpretation and empirical modeling are needed to determine the relative depths. The device (Fig. 2) generates alternating current through the supply dipole to the ground With the help of a signal generator 34. Measuring device 35 includes those indicated above in FIG. 1, potential electrodes, a receiving cable, and multichannel amplification, analysis, and output circuits are sequentially arranged, and the signal generator contains a digital signal generator 36 that controls the current signals in the generator dipole in frequency, amplitude, or duration. This control signal is then fed to a preamplifier 37 for amplification. The signal from the output of the preamplifier 37 subas lia the input of the amplifier 38 power (current generator). The above digital signal generator allows to receive the signal at the output of any form: sinusoidal, rectangular, stepped, sawtooth, etc. The advantage of the digital signal generator is that it is possible to accurately repeat the shape and duration of the signal. As the above preamplifier and power amplifier, you can choose any Industrial current depending on the needs in accordance with specific tasks, and the characteristics of the amplifiers depend on the input signal required. In general, amplifiers should work in the range of approximately 0.005 to 5 Hz with an output power of about 1 kW with a minimum dual amplitude of voltage of 500 V to measure an EF to a depth of several tens of meters. A higher voltage and signal strength may be desirable. at lower frequencies, especially for more in-depth study. A rotary amplifier, i.e., an amplifier of 38 mops needles in today's field observation systems, is used. a kind of dc generator. Current signal from the current generator core, i.e. the power amplifier 38 is supplied directly to one of the current electrodes and through the current collector 39 to the other. The current collector 39 serves to release a reference voltage proportional to TOKV at the output of the current generator for passage through line 40 to the measuring device, as will be described below. The current collector 39 is an inductive device. Each of the current electrodes of the generator dipole create as follows. On the surface of the earth they dig out a rock or a group of rocks in certain places on the surface, impregnate the rock with salt water, lay out the diodes and walls of the rock:} with an electrically conductive foil, for example, aluminum, put the soil out back

foil and attach the appropriate connecting cables to supply a current of ppi using a detachable clip or crocodal. In the measuring device measurable

the potential and each of the potential electrodes are supplied through a separate wire of a multicore receiving cable and through a connecting cable to the input of a six-channel amplifier 41. Each channel of amplifier 41 may have the same design and a TNP selected from many well-known standard amplifiers. The most important requirements for amplifiers are: differential output, high sensitivity and high interference suppression ratio in co-operation mode, exceeding 100 dB. Amplifier 4 is represented as a six-channel switch. However, it is possible to specify a different number of channels according to the structure of the system and the position of one H) 1x sensor, the size of which depends on the choice. The six-channel system was recognized as practical for work in molar conditions, where the described system will work. Each channel amplifier 41 receives a differential signal from the corresponding successive pairs of potential electrodes. In this way,

The sensed Ei-Er potentials will be amplified at the differential amplifiers through six corresponding channels of amplifier 41. The output signal of the output of amplifier 41, containing six amplified potential differences (potential Ej-E), is fed through a multicore cable 42 to each of the seven channels. {digital digital average 43 and a seven-channel magnetic recorder 44. Seven-channel digital average

43 contains ps as far as blocks like Bud, em is lower, with six channels receiving a loop signal from the output of amplifier 41, and the seventh channel receives a reference signal from the specified detector. This current collector may, for example, be a magnetic modulator that produces a voltage on line 40, which is proportional to the actual current applied to earth. The reference voltage on line 40 also enters the channel of magnetic recorder 44. Magnetic recorder

44 can be a widespread multichannel tape recorder with a frequency module of a type that is quite widespread in geophysical prospecting.

FIG. 3 schematically shows a part of the receiving cable 20, in particular, the new internal wiring of the contacts 23, which allows for the rapid non-growth of the monitoring system station without having to: 1 × 1 H1 to: 1. Each of the contacts

23 has identical wiring and each of the lengths of cable 20 and connecting cable 24 also have identical wiring. Each of the connecting contacts 23 contains bent connectors, the internal contacts of which are arranged in a shahmatny order and marked with letters А-В, В-С, С-Д etc., and the connection leads back to contact A. Specific potential electrode 2 B station and its wire 2 .; also connected to the JA connection. This configuration is in each connecting contact 23. It allows truck 13 (FIG. 1) to continuously move J from one position to another for the Next floor in sequence and each time the connection cable 24 with the first connection contact 32 in a linear arrangement of the positions will confirm that the seven potential potentials from the arrangement of the positions are present at contacts A to G at the end of the connecting cable

24 from the side of the truck for entry into the differential amplifiers of the measuring device 41. Thus, those potential electrodes that are located at a given number of positions from the truck 13 will always appear at the same inputs of the measuring device 41,

A seven-channel digital averager 43 with the read circuit shown in FIG. 2 is shown in more detail in FIG. 4, Thus, digital averager 43 includes an input multiplexer 45, the signal to the input of which is supplied from line 40, and a multicore cable 42. In other words, the input control signal from the current collector 39 is fed through a wire 40 to the input of one channel of the multhexor 45 and the signal from the output

the differential amplifiers of the measuring device 41 are fed to the corresponding serial inputs of the multiplexer 45. The multiplexer 45 may be a known time-division multiplexer, providing multiplexed, in. The analog signal coming over line 46 to the buffer amplifier 47, the multiplexing and switching speed, is controlled by the input signal on the wire 48 from the multiplex counter and the control circuit 49. which is in. the turn is controlled by a signal from the system output. 50 clock frequency counter and 51 clock frequency generator. In systems of the type described, generator 51 is a known generator circuit operating with. frequency of 4 MHz, which. then it is divided by a clock counter 50, the signal from the output of which is fed to a multiplex counter and a control circuit, while the predetermined multiplexing frequency is de-energized. A signal from the output of the clock frequency counter 50 is also supplied to the measurement circuit 52 counting circuit, which can be controlled by the switch 53 for the duration of the cycle to receive the output signal via the wire 54 to the program control unit 55. The program 55 of the control program operates with a clock with a clock counter 50 upon receipt of a clock output signal through the wire. The software control unit 55 provides control and synchronization of the entire device. Thus, the device 55 of the central or programmed control starts a digital signal generator 36 (FIG. 2) to start the operation of the field part of the system. The cycle duration .53 switch is a knob on the operator console that serves to control the number of the number of cycles on the counter 52 by 4eio-controlling the duration of the operation of the signal generator system 34. The measured signals after multiplexing and passing through the buffer amplifier 47 are fed to an analog-to-digital converter 56, from which digital signals are fed to the line 57 and a multiplier circuit 58, as well as to the multiplier-register 59 of the multiplier, which sets the multiplication factor in the multiplier 58. Multiplied digital the values are then hindered in the product register 60 for shifting in the serial adder 61 and in the serial serial memory 62., Multiplier 58, the product register 60, the serial adder 61 and the In other words, memory 62 actually implements digital data processing of all channels of multiplexed data from an incoming signal of a digital-to-audio converter 56. Thus, each data channel is multiplied and integrated in a given time interval in real time, Scheme 63 is a well-known schema, in which the multiplexed data blocks following each other are first multiplied by successive signals from the output, register multiplier 59 and multiplier 58 by the given coefficient sootvetstvuyuschegoraspolozheni for storing channel time dann1H in register 60 works. Thereafter, the data blocks in the sequential code, which are output from the product register 60 through the serial adder 61, are passed through this time interval, while the serial memory 62 non-irregularly shifts the accumulated data back in a predetermined time interval. The time-correlated current control signal, as well as the correlated signal for each of the potential difference cycles (E, -Ee), is fed through line 64 to the input of display indication circuit 65. The matching circuit 63 is a device for processing field measurements of frequency measurements, since one output signal will produce an ALT value, a proportional relationship of voltage to a voltage with a zero shift of the current control path, and the other channels provide values. proportional mutual communication with the Zero shift of the current control path with each of the potential difference paths. The timed digital output data is then reproduced by the anchoring reader 66. Thus, the first transformed data on the .57 line is applied to the analog-to-digital converter register 67, after which they are shifted on the display selection circuit 65, which also received time-linked data on the 64 link. The switch - display selection switch 68 is intended to control the display selection 65 - to set in the channel selection circuit 69 or analog-digital data; Cx: the cam selection selector 69 contains a logic circuit that, when controlled from the manual channel selection switch 70, selects The required information channel for the output signal is the line 7J. In other words, using the channel selection switch 70, the data of either the current control path or one of the selected potential paths on line 71 is selected. The output signal on line 71 is first shifted by the lower order and in order to provide an appropriate Baiffle transform, it is necessary to revise the sequence inverting circuit 72. The sequence inversion circuit 72 contains a known register circuit, for example, a trigger register, which accumulates digital data at the input in the forward direction and inverts them so that the output data of the selected channel on the wire 73 is located forward for the input of the converter 74 from the binary code to the POD code. Thus, the converter 74 converts the binary sequence into a digitizer, the sequence in the BCD code of the Li.II .75, the data in the BCD code on the line 75 is then transferred to the register 76 ind ation for Sliding ha and for controlling the read control circuits 77, the gate devices 78 read the digital-emitting diodes. The data in the BCD code on line 75 is also fed to an exponential counter circuit 79, which, in accordance with the magnitude count, produces a periodic signal to the read control circuit 80 to control another light emitting diode device — the exponential reading device 81. The field layout in FIG. 1 is inherently a multi-channel, induced polarization measurement system that allows simultaneous measurement with a plurality of spaced-apart potential electrodes at a given time. The duration is selected in accordance with the requirements of a particular observation, terrain characteristics, electrical noise, etc. After being placed on the equipment profile, the current is supplied to the ground via the current electrodes 16 and 17. The control signal is excited by a digital signal generator 36 (FIG. 2) and fed through a preamplifier 37 to a rotary power amplifier or a current generator 38. generarov1 |) and a stable sinusoidal signal with a frequency in the range of 0.005 and 8 Hz. It is assumed that there will be such applications where the applied current signal will have a predetermined frequency, linearly varying in time, for studies related to the study of the frequency characteristics of various materials. The duration of the input voltage corresponding to the current is different, depends on the requirements of specific measurements and is directly related to the required averaging time required by the measuring device 35. Usually, a current between current electrodes 16 and 17 is excited with a frequency of 0.1 Hz time of about 10 minutes, during which time the EI-Eg voltages are continuously measured from the system of differential electrodes, which in turn enter multiplexer 45 (Fig. 4) and are tied in time using matching circuit 63 ( f 4 g) and then induced by means of the read circuit 66 (FIG. 4) and (or) zapistayuts pas multichannel analog recorder 44 (FIG. 2). In the following, measurement cycles of the same length are used at a frequency of input current, current of 1.0 Hz, and then of other frequencies selected within the limits of the extremely low frequencies indicated above. The processing performed by digital averaging circuit 43 is equivalent to passing a signal through a filter with a very narrow passband corresponding to the frequency of polarizing current. The quality factor of the filter will increase with increasing recording time. Thus, for each measurement cycle at a given frequency, a number of samples (seven in the example shown) will be read using a digital average, which are proportional to the current signal, as well as the potential difference associated with the excitation signal. The digital values read by the digital readout devices 81 are then stored by successive switching of the channel selection switch 70 to calculate the resistances, the frequency effect and the metal factor. For example, the parameter of induced polarization in the frequency method EP or frequency effect (SE) is expressed by the following formula:. 1 WWH 1 X 100%, where it means mutual correlation; fp and fin - two input frequencies (low and high); V is the potential difference between the selected type electrodes, and I is the input current. In addition to the SE values, from the well-known computational and / or computational algorithm using a computer one can easily GET other related parameters: resistivity, metal factor and other specialized parameters used in various two-dimensional and three-dimensional representations;. FIG. Figure 5 shows another variant that may well show the general tendency of using devices of the method of induced polarization. This is because there are various types of mini-computers with increased reliability, with the ability to work in mobile field installations or cars. FIG. 5 shows the field circuit 82, the working components of the power supply system 83 and the measuring device 84 are the same as shown in FIG. 2. The main difference is that a specialized type of computer 85 can be used to control the generation of an input current signal, as well as perform cross-correlation and digital calculations, printing or other selected output of the processed polarization parameters. The computer 85 can be used to quickly calculate all the data in the constant-current and alternating-current VI method.

The specified computing equipment can be a universal machine with low speed and limited memory;

It is also possible to use various specialized computers built specifically for use in geophysical prospecting. In any case, the use of computers is much easier to study induced polarization due to the fact that the system can be fully automated and synchronized in all respects, i.e. starting with energizing the required input current signal, including intermediate stages of mutual correlation and increasing the signal-to-noise ratio, and ending with the final calculations of information in new formats and dependencies ..

This means high speed and reliability when determining the presence and location of deposits.

The use of the proposed device makes it possible to detect relative data of layers below the surface of the earth, the information has a higher reliability due to the increased ability to differentiate in the presence of noise and natural disturbances. Simultaneous processing of sequentially and spatially related data over time allows averaging and increases productivity.

labor.

Claims (2)

1.Hallof R.G. ludmed polarization case histories and technical papers. Me Phar. Geophysical Ltd, 1970. 2. Komarov B. H. Electromagnetic prospecting by induced polarization. L., Nedra, 1972, p. 192, 198-206 (prototype). 28 y / / ...... .k - s .------- / |:: ...-. Hee ..: - / 7 Fig, f: 36 J7 / 0 G8 J7 4d four / 42 z / c with / X / P Q cf o g 4. J. .1 J. f L i; / 1 // itvl corner 2 83 ff I / / fff 7