Multi-functional Electro-method Instrument is a special equipment for rapid underground water source detection and hydrogeological engineering geological survey, which is an intelligent electro-metrological workstation integrating transmitter, receiver, data processing, data storage and data display. The multifunctional electro-methodometer described in this section can be directly used for the measurement of resistivity method and excitation polarization method, and it can display the measured values of apparent resistivity, apparent polarizability, half decay time, attenuation degree, deviation degree, cumulative sum of polarizability, natural potential, power supply current and primary field on the same screen. The system adopts modern embedded system technology, large-scale integration technology, high-precision conversion technology, so that the multifunctional electro-methodometer in the field exploration to realize the integration of signal acquisition, data processing, and imaging display.
I. Basic structure and working principle of DWZ-6A multifunctional electro-methodometer
Multifunctional electro-methodometer is widely used to search for groundwater and solve the problem of industrial and agricultural water and life water by using apparent resistivity and excitation polarization parameters. It can be used to search for fracture zones, trap columns, air-mining zones, landslides and so on. It can be used for hydrogeological survey, engineering geological survey, environmental geological survey, and also can be used for mineral survey, energy survey, geothermal survey, urban physical exploration and so on.
As shown in Figure 6-1-1, DWZ-6A multifunctional electrodynamometer is an intelligent electrodynamometer controlled by ARM, the electrical signal is input from M, N, after impedance transformation and filtering, through the double T trap and low-pass filtering, filtering out the utility interference and high-frequency interference signal. After amplifying the weak signal, the analog-to-digital converter converts the analog signal into a digital quantity, which is stored in the data memory. The transmit control signal is isolated by high voltage to drive the power supply bridge circuit for forward and reverse power supply. The current signal is sampled by the standard resistor, amplified and filtered by isolation, amplified by the programmable amplifier and then time-shared for analog-to-digital conversion and storage.The ARM control system takes out the primary field potential difference, the secondary field potential difference, and the current data from the data memory, calculates and processes them, and then displays the results of the processing and stores them. Finally, the data is copied to U disk or transferred to computer. The keyboard is used to input various parameters. The control system can also monitor the working status of the instrument, monitor the fault status of the instrument, when the instrument internal or external failure (such as AB short circuit), the instrument automatically block the power supply circuit to stop power supply and alarm display.
Figure 6-1-1 DWZ-6A multifunctional electrophysical instrument principle block diagram
Two, DWZ-6A multifunctional electrophysical instrument of the hardware circuit design
(a) the overall framework of the hardware
DWZ-6A multifunctional electro-methodometer hardware circuit overall framework shown in Figure 6-1-2, the instrument mainly consists of sending device, receiving device and its main control unit. The main control adopts ARM7 S3C44BOX chip, when need to carry out the exciting electric data acquisition, the main control sends control commands to the IPM module to realize the power supply from the power supply point A, B to the earth power supply. At the same time in the measurement electrode M, N to receive the excitation signal, through the excitation signal processing circuit, into the 24-bit AD converter CS5532 converted to digital signals, ARM7 master control and CS5532 information interaction to achieve the converted data reading, storage, processing and display.
Figure 6-1-2 overall hardware structure
(B) DWZ-6A multi-functional electropneumatic transmitter circuit design
The block diagram of the excitation transmitter circuit is shown in Figure 6-1-3, which is the same as that of the DWZ-6A multi-functional electropneumatic transmitter. shown. Power part of the IPM PowerEX intelligent power module: PM10RSH120, the maximum controllable voltage of 1200V, controllable current of 10A, the highest value of the actual application of 2/3 as the instrument's actual voltage and current limit. The power of this stimulated transmission circuit is tested to be up to 900V@6.7A, i.e. 6kW, so the supply voltage range of the high-voltage power supply battery pack is from 0 to 900 V. In order to realize the control of strong power by weak power, it is necessary to isolate the strong and weak power from each other, and the control signals and the IPM module are isolated by using the multi-slice opto-coupler devices, HCPL-4504 and PC817. In the sending circuit from the A, B end to the underground power supply, the need to monitor its power supply current, the use of high-precision 0.01 Ω sampling resistor Rs will be converted to voltage current sent to the AD202, AD202 is a high-precision isolation amplifier, which through the transformer coupling will be isolated from strong and weak circuits, and will be amplified signal Vout to the exciting power receiving circuit.
Figure 6-1-3 DWZ-6A multifunctional electrodynamic transmitter circuit block diagram
(C) DWZ-6A multifunctional electrodynamic receiver circuit design
Figure 6-1-2, in addition to the IPM and high voltage circuitry, the IPM and high voltage circuitry can be used to receive the signal. -2 in addition to the IPM and high-voltage packages in addition to other parts of the radical power receiving circuit block diagram. The main control adopts ARM7's S3C44B0X chip, and its storage part extends NorFlash chip SST39VF16 (storing program), NandFlash chip K9F2808 (storing data) and SDRAM chip HY57V2816 (program running space). In order to realize human-computer interaction, a keyboard is used for information input and an LCD monitor (320×240 pixels) for information display.The IPsignalprcessingcircuit mainly consists of a lightning protection circuit, a preamplifier, a 50Hz trap, a differential amplifier, and a low-pass filter, etc. The excitation signal is passed through the module and enters into the 24-bit programmable gain A/D converter chip, CS5532.The DAC chip, CS5532, is also used. The analog signal output from the DAC chip AD5660 is superimposed on the input excitation signal to realize the automatic zeroing of the analog circuit. When the need to upload data to the host computer, you can use the USB (using PDIUSBD12 chip) interface docking, the host computer will recognize the excitation instrument in the memory for a USB flash drive, but also NetWork interface (RTL8019 chip) to achieve the host computer and the excitation instrument information interaction.
Three, DWZ-6A multi-function electrophotometer software program design
DWZ-6A multi-function electrophotometer selected uClinux as the operating system, uClinux is derived from the Linux kernel, inherited most of the characteristics of Linux. Under the guarantee of the GNU General License, users running the uClinux operating system can use almost all LinuxAPI functions. Due to its tailoring and optimization, uClinux has the advantages of small size, stability, good portability, excellent networking capabilities, complete support for various file systems, and a rich set of API functions.
The focus and difficulty of embedded software development in DWZ-6A multifunctional electrophysical analyzer lies in the software part of the operating system cut, driver and application program embedded. While the cut and transplant method of uClinux has universality, we will not repeat here.DWZ-6A multifunctional electrophysiological instrument in the device driver and application software mainly includes the system on the keyboard, LCD, CS5532, data processing and data upload management and control. Keyboard, LCD is the input and output devices of the whole system, which is the main way of human-computer interaction. The data display program can draw the curve of polarization rate and resistivity on LCD. Data uploading is carried out through USB and network mode. The following focuses on the data acquisition and data processing programs.
(I) Data Acquisition Program Design of DWZ-6A Multifunctional Electrometer
Data Acquisition Program Design is mainly to control CS5532 to realize high-precision acquisition of data, and this part includes the underlying driver and application program of CS5532 in uClinux system. When writing the driver program for CS5532, according to the technical documents of the chip, write the program according to the working time sequence of the chip and combine with the needs of the excitation instrument. The system control of CS5532 mainly includes the control of sampling rate and A/D gain, and the underlying driver of CS5532 mainly includes the simulation of SPI, initialization of CS5532, filling the file ____operations structure of the character device driver of uClinux system, timing interrupt, external interrupt, etc. The driver of the character device of uClinux system is mainly writing subfunctions and filling the subfunctions. The main thing is to write sub-functions and fill the various fields of file_operations. According to the actual needs of the excitation instrument, the CS5532 device driver only needs the open, ioctl, release, and read functions in the file_operations structure. the operation of the CS5532 application program on the underlying driver includes the opening of the device file, reading and writing of the device file, and the closing of the device file. The main function calls are as follows:
Geophysical water search method technology and instrumentation
(II) DWZ-6A multifunctional electrodynamic instrument data processing program design
DWZ-6A multifunctional electrodynamic instrument in the design of geophysical electrodynamic method of a variety of devices (in the ladder, bathymetry, the joint profile) acquisition methods, built-in various kinds of electrodynamic etc.), built-in acquisition parameters commonly used by various devices, and intelligent processing of natural potential, primary potential, supply current, apparent resistivity, apparent polarizability, half-life time and other geophysical parameters, while the data processing program is based on the geophysical method of in-depth processing of the data collected by CS5532, which calculates the above geophysical parameters. Among them, apparent resistivity and apparent polarizability are important parameters in the excitation meter, and the formulae of apparent resistivity ρS and apparent polarizability ηS are as follows:
Geophysical water searching method technology and instrumentation
Please refer to the second chapter for the principles and formulae of the main parameters in the DWZ-6A multifunctional electrodynamic method meter.
There is a certain noise in the signal collected by DWZ-6A multifunctional electro-methodometer, although filtering and denoising have been carried out in the analog circuit, but the performance of the analog filter is limited, in order to improve the quality of the geophysical parameters in the designed excitation electro-methodometer, a software digital filter has been added to the data processing program, which is a 50 Hz band-stop type FIR It is a 50 Hz band-reject FIR filter.
In order to improve the exploration efficiency, suppress the interference signals in the field measurements and optimize the measurement accuracy of the apparent polarization rate, the alternating positive and negative rectangular pulse currents are used to supply power during data acquisition. Positive power supply, negative power supply measurement of the secondary potential difference and the total field potential difference are: △V2p, △V2n, △Vp, △Vn, so DWZ-6A multifunctional electro-methodology instrument used in the visual polarization rate calculation formula is as follows:
Technology and Instrumentation for Geophysical Water Searching Methods
Above the secondary potential difference is measured in the sender circuit after a certain time delay after the power failure. The above secondary potential difference is the result of delayed measurement for a certain period of time after the power failure of the sending circuit, so there is a certain relationship between the secondary potential difference and the delay time. Different models of multifunctional galvanometer due to different delay time, the results of the measurement are not the same, DWZ-6A multifunctional galvanometer set up five kinds of power failure delay time, so it can deal with five kinds of visual polarization rate, and also can manually enter the delay time to get the expected power failure delay of the visual polarization rate parameters.
Four, DWZ-6A multifunctional electro-methodometer function and technical indicators
DWZ-6A multifunctional electro-methodometer is to adapt to the needs of water search and the development of a new intelligent multifunctional electro-methodometer. It can be used for water search, geothermal search, mineral search, and geological investigation in engineering geology, environmental geology, energy geology, etc. DWZ-6A Multifunctional Electrometer is equipped with small power transmitter, and it can also be matched with high power transmitter of more than 10kW, and it can be used for deep-searching in the way of short conductor. The external high-density multi-way electrode converter can be used for high-density electro-method measurement, and it is used for hydro-geological survey, engineering geological survey and environmental geological survey when the sending power is small. With more than 10kW high-power transmitter can carry out high-power or ultra-high-power high-density electric method measurement, used for deep rapid search for minerals. At present, there is no second international development of extra-high-power high-density electrical measurement system (generally only a few hundred watts).DWZ-6A multifunctional electro-methodometer has more functions, good performance, more parameters, high power, high technical indicators, the application of a wide range of characteristics.
The parameters measured and calculated by DWZ-6A multifunctional electrophotometer are: apparent resistivity, apparent polarizability, half decay time, attenuation degree, integrated parameter, deviation degree, excitation ratio, relative decay time, charging rate.
The main technical indexes of DWZ-6A multifunctional electrophotometer:
Voltage measurement range: ±10V
Voltage measurement accuracy: ±0.2%
Current measurement range: ±10A
Current measurement accuracy: ±0.2%
Input impedance: more than 60M Ω
Self-electricity compensation range: ±2000mV
50Hz suppression: greater than 80dB
Maximum supply voltage: 1200V
Maximum supply current: 10A
Power supply time: 1 ~ 99s range can be selected
Interface: USB, RS232
Working temperature: 10 ℃ ~ 10A
Working temperature: 10 ℃ ~ 10A
Working temperature: 10 ℃ ~ 10A
Working temperature: 10 ℃ ~ 10A Operating temperature: -10℃～＋55℃
Operating humidity: <95%RH
Section II EH-4 electromagnetic instrument
I. EH-4 electromagnetic imaging system method principle
EH -4 electromagnetic imaging system belongs to a combination of controllable sources and natural sources of a geomagnetic probing system. Deep structures are imaged by natural background field sources (MT). Shallow formations are imaged by a portable low-power transmitter that transmits an artificial electromagnetic signal from 500Hz to 100kHz to compensate for the lack of natural signals, resulting in high-resolution imaging.
Taking the earth as a horizontal medium and the earth's electromagnetic field as a plane electromagnetic wave projected vertically into the subsurface, the mutually orthogonal components of the electromagnetic field can be observed on the surface as Ex, Hy; Hx, Ey. The resistivity of the medium can be determined by measuring the mutually orthogonal components of the electric and magnetic fields. The formula is:
Geophysical water search method technology and instrumentation
The formula: f is the frequency, unit Hz; ρ is the resistivity, unit Ω-m. Because the underground medium is not uniform, and thus the calculated value of ρ is called the apparent resistivity value. The depth of detection is theoretically a skinning depth, which is calculated as
Geophysical water search method technology and instrumentation
δ is the skinning depth. The above formula shows that the penetration depth of electromagnetic wave increases with the increase of resistivity and the decrease of frequency.
Two, EH-4 instrument system
EH-4 system is mainly composed of three major parts: transmitting, receiving and data processing. The working principle of the system is shown in Figure 6-2-1, and the field work arrangement is shown in Figure 6-2-2.
Figure 6-2-1 EH -4 system's working principle diagram
Figure 6-2-2 EH-4 field working arrangement
(I) Receiving part
Mainly consists of the main unit, preamplifier (AFE), magnetic sensors, with buffer electrode and its ancillary equipment.
1) The mainframe is the center of the whole system, which is mainly used for file management, data acquisition and data processing. It uses IBM portable computer, memory 8MB, hard disk 810MB, analog-to-digital conversion 18 bit, digital processing 32 bit floating point, liquid crystal VGA display, working temperature 0 ~ 50 ℃.
2) The preamplifier filters and amplifies the collected electromagnetic field signals, which are transmitted to the host computer through the transmission line. Set up four channels (two electric channels, two magnetic channels), built-in rechargeable battery.
3) The magnetic sensor is mainly used for collecting magnetic field information, and observes the frequency response range: standard configuration (BF-1M type), 10Hz～100kHz; low frequency configuration (BF-2M type), 0.1Hz～1kHz.
4) The electrode is mainly used for receiving electrical information. The standard configuration is BE-16 type buffer electric sensor with 16m cable and titanium steel electrode; the low-frequency configuration is BE-50 type buffer electric sensor with 50m cable and CuSO4 unpolarized electrode.
(II) Transmitting part
The transmitting part is mainly composed of transmitting antenna, transmitter and 12V DC power supply. The transmitting antenna adopts two orthogonal semicircular antennas of novel conception, which is one of the unique features of this system. The transmitter itself has a transmitting frequency of 500Hz to 100kHz, which is matched with the impedance of the transmitting antenna. Different transmitter antennas are used for different frequencies. With the standard antenna configuration, the transmit frequency is 1 to 64 kHz; with the low-frequency configuration, the transmit frequency is 500 Hz to 32 kHz.
The positioning of the transmitter is critical. Because the EH-4 system's data processing software to the field source away from the measurement point (i.e., far field area) as a prerequisite. A transmitter that is too close or too far away will have a great impact on the test results and even produce false anomalies, so the system's transmitter can be moved quickly and easily, which in turn is one of the system's unique features. In principle, the distance between the transmitter and the receiver is taken as 3 to 4 times of the deepest target detected by the controllable source. Theoretically, the transceiver distance (r) should be the lowest operating frequency "skinning depth" δ three times, that is
Geophysical water search methodology, technology and instrumentation
The formula: r is the distance between the transceiver; δ is the skinning depth; ρ is the earth's average resistivity; f is the lowest operating frequency.
(C) Data acquisition, information processing
1. Data acquisition
The data acquisition method of this system is time-domain acquisition, and then Fourier transform, converted to frequency-domain signals, i.e., firstly, the electromagnetic signals of 4 channels (2 electric channels, 2 magnetic channels) are collected in the time-domain, and then Fourier exchanged, and then converted to the real component of electromagnetic signal, the imaginary component of power spectrum, and visual resistivity, phase difference, correlation coefficient, etc. are calculated from the spectrum.
For the standard configuration, the entire sampling frequency band is divided into three bands: 10Hz to 1kHz (band 1); 300Hz to 3kHz (band 4); 1.5 to 99kHz (band 7). The number of superimpositions can be set artificially for each band. The number of superimpositions is confirmed according to the quality of the signal; good signal quality results in fewer superimpositions. Each frequency sampling is further divided into three segments, the sampling time of the transmitter field part is 20ms for each segment, with 4096 sampling points, and each segment undergoes a Fourier Transform, whose final number of frequency points is 60. For the low-frequency configuration, the sampling method is similar to the standard configuration, only the sampling time is lengthened accordingly. The entire frequency band is carried out in two parts (50Hz to 1kHz; 0.1Hz to 75Hz).
2. Output Files
There are four output files for this system regardless of the configuration, i.e., @File, Y-File, X-File, and Z-File for the standard configuration and @L-File, V-File, U-File, and W-File for the low frequency configuration. The @ (or @L) file is the measurement information file. It mainly includes operating frequency and start file number, transmitter and receiver position, x and y direction dipole length and hexadecimal internal gain setting. y (or V) file is a binary timing file. x (or U) file is a mutual power spectrum file, each line consists of 19 columns, each column length 11 characters, unit is H-nT, E -V/km, f-Hz. z (or W) files are text impedance files. Each frequency consists of 12 lines, each column has 8 characters, this file is the final processing file. The main contents are frequency, scalar apparent resistivity in the x and y directions, phase, correlation, and impedance elements for the 8 real and imaginary components.
3. Data processing
There are two kinds of data processing: real-time processing and follow-up processing. Real-time processing, according to the apparent resistivity, phase, correlation and amplitude curves given by each measurement point, real-time analysis of data quality. For some unreliable data can be removed from the curve and then continue to measure, or the data quality of the whole curve is too poor, take measures to implement repeated measurements. After completing the continuous observation of the whole measurement line, the EMAP method (which can effectively eliminate the static effect) can be used in the field to give a grayscale map of the results of the proposed two-dimensional inversion interpretation. Follow-up processing is a work completed indoors after the field work, which generally includes two elements: one is to adjust the correlation coefficient and filter coefficient of the field data on the mainframe computer or to reprocess the time series information (Y or V files) such as selecting or eliminating them one by one. The influence factors are minimized and useful anomalies are highlighted to achieve the purpose of use. In addition, on the basis of the above work, the final processed result file (Z or W) is copied to a PC for further quantitative interpretation and two-dimensional inversion processing, and color mapping.
Third, the main parameters of the EH-4 electromagnetic imaging system
Working principle: natural and artificial magnetic earth current tensor field
Standard frequency range: 10Hz ~ 100kHz
Transmitter: TxIM2 type transmitter with vertical antenna coil
Frequency: 500Hz to 70KHz
Impulse: 400Amp-m2
Antenna size: 2 x 4m2 vertical crossover coils
Power supply: 12V, 60Ah battery
Electrodes: 4 x BE-26 type effective HF dipoles with buffers and 4 SSE stainless steel electrodes, 26m cable
Magnetic rod probe: 2 BF-1M magnetic induction rods (10Hz to 100kHz), 10m cable
Analog terminal: 1 AFE-EH-4 analog signal conditioner, which transmits the electrode's Analog terminal: 1 AFE-EH-4 analog signal conditioner, which transmits the signals from the electrodes to the acquisition unit
Bandwidth of a pair of rods: DC-96kHz
Processor: 32-bit floating point
Display: LCD VGA
Printer: Built-in 4" (11cm) printer
Power supply: 12V, 40Ah
Operating temperature: 1.5°C to 1.5°C. /p>
Operating temperature: 0 to 50°C
Instrument case: portable, rugged, waterproof
Options:
Configuration of StrataViewTM
Low-frequency MT Magnetic Bar: 0.1 to 1kHz
Electrodes: 4 effective high-frequency BE-50 type with buffer Dipole and 50m cable
High power antenna: Frequency range: 300 to 35KHz
Impulse: 6000Amp-m2
Antenna size: 2 x 45m vertical cross coils
Data Acquisition Unit:
Number of Channels: 4 Channels (2 electric, 2 magnetic)
Built-in computer: IBM compatible 80486 CPU 8MbRAM and floppy disk.
Hard disk: 1.2G or larger
Analog-to-digital conversion: 18 bits