Multifunctional electric water finder

Multifunctional electrical prospecting instrument is a special equipment for rapid detection of underground water sources and hydrogeological engineering geological exploration. It is an intelligent electrical measurement workstation which integrates transmitting, receiving, data processing, data storage and data display. The multifunctional electrical instrument introduced in this section can be directly used for resistivity and induced polarization measurements, and can display the measured values of apparent resistivity, apparent polarizability, half-life, attenuation, deviation, 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 and high-precision conversion technology, which makes the multifunctional electrical prospecting instrument realize the integration of signal acquisition, data processing and imaging display in field exploration.

First, the basic structure and working principle of DWZ-6A multifunctional electrical method instrument.

Multifunctional resistivity meter is widely used to find groundwater by apparent resistivity and induced polarization parameters, and solve the problems of industrial, agricultural and domestic water use. It can be used to find fault zones, collapse columns, mined-out areas, landslides and so on. It can be used for hydrogeological exploration, engineering geological exploration, environmental geological exploration, mineral exploration, energy exploration, geothermal exploration, urban geophysical exploration and so on.

As shown in Figure 6- 1- 1, DWZ-6A multifunctional electrical instrument is an intelligent electrical instrument controlled by ARM. Electrical signals are input from M and N, and after impedance transformation and filtering, they are filtered by double T-notch and low-pass filtering. After the weak signal is amplified by the analog-to-digital converter, the analog signal is converted into digital quantity and stored in the data memory. After the control signal is isolated by high voltage, the power bridge is driven to supply power forward and backward. The current signal is sampled by standard resistor, isolated, amplified and filtered, amplified by program-controlled amplifier, and then stored in time-sharing conversion. The ARM control system takes out the primary field potential difference, secondary field potential difference and current data from the data memory, calculates and processes them, and then displays the processing results and stores them. Finally, copy the data to a USB flash drive or transfer it to a computer. The keyboard is used to input various parameters. The control system can also monitor the working state and fault state of the instrument. When there is a fault inside or outside the instrument (such as AB short circuit), the instrument automatically blocks the power supply loop to stop power supply and gives an alarm display.

Fig. 6- 1- 1DWZ-6A principle block diagram of multi-function electrical appliances

2. Hardware circuit design of DWZ-6A multifunctional electrical appliance.

(A) the overall hardware architecture

The hardware circuit structure of DWZ-6A multifunctional electrical prospecting instrument is shown in Figure 6- 1-2. The instrument is mainly composed of transmitter, receiver and its main control unit. The main controller adopts S3C44BOX chip of ARM7. When IP data needs to be collected, the main controller sends control commands to IPM module to realize power supply from A and B power supply points to the earth. At the same time, IP signals are received at the measuring electrodes M and N, and sent to the 24-bit AD converter CS5532 through the IP signal processing circuit, and then converted into digital signals. The main controller of ARM7 interacts with CS5532 to read, store, process and display the converted data.

Figure 6- 1-2 overall hardware architecture

(2) The design of DWZ-6A multifunctional electric instrument transmission circuit.

The block diagram of IP transmission circuit is shown in Figure 6- 1-3. The high-voltage part adopts IPM intelligent power module of PowerEX company: PM 10RSH 120, the highest controllable voltage 1200V, and the controllable current 10A. In practical application, 2/3 of the highest value is taken as the upper limit of the actual voltage and current of the instrument. The actual test shows that the power of this IP transmission circuit can reach 900 V @ 6.7 A, that is, 6kW, so the power supply voltage range of high-voltage power battery pack is 0 ~ 900 V. In order to control strong current and weak current, it is necessary to separate strong current from weak current. The control signal is isolated from the IPM module by using multiple optocouplers HCPL-4504 and PC8 17. When the transmission line supplies power from terminals A and B to the underground, it is necessary to monitor the power supply current. A high-precision sampling resistor Rs of 0.01Ω is used to convert current into voltage and send it to AD202. ad 202 is a high-precision isolation amplifier, which isolates strong current from weak current through transformer coupling and sends the amplified signal Vout to the IP receiving circuit.

Fig. 6- 1-3dwz-6a Block Diagram of Transmitting Circuit of Multifunctional Electrical Apparatus

(3) The design of receiving circuit of DWZ-6A multifunctional electric measuring instrument.

In Figure 6- 1-2, except for IPM and high-voltage packet, all other parts are IP receiving circuit block diagrams. The main controller adopts S3C44B0X chip of ARM7, and the storage part extends the NorFlash chip SST39VF 16 (storage program), NandFlash chip K9F2808 (storage data) and SDRAM chip HY57V28 16 (program running space). In order to realize human-computer interaction, the keyboard is used for information input and the LCD (320×240 pixels) is used for information display. IPsignalprcessingcircuit mainly includes lightning protection circuit, preamplifier, 50Hz trap, differential amplifier and low-pass filter. After this module, the IP signal enters the 24-bit programmable gain A/D conversion chip CS5532. The analog signal output by the DAC chip AD5660 is superimposed on the input ip signal to realize the automatic zero adjustment of the analog circuit. When it is necessary to upload data to the upper computer, the USB (using PDIUSBD 12 chip) interface can be used for docking, and the upper computer will recognize that the memory in the ip instrument is a U disk. At the same time, the network interface (RTL80 19 chip) is used to realize the information interaction between the upper computer and the ip instrument.

Thirdly, the software program design of DWZ-6A multifunctional electrical instrument.

The DWZ-6A multifunctional electrical instrument chooses uClinux as the operating system, which originates from the linux kernel and inherits most of the features of Linux. Under the guarantee of GNU general license, users running uClinux operating system can use almost all LinuxAPI functions. After cutting and optimization, uClinux has the advantages of small size, stability, good portability, excellent network function, full support for various file systems, and rich API functions.

The key and difficult point of DWZ 6A multifunctional electric instrument embedded software development lies in the cutting, driving and embedding of some software applications. However, the cutting and transplanting methods of uClinux are universal, so I won't go into details here. The device driver and application software of DWZ 6A multifunctional electrical instrument mainly includes keyboard, LCD, CS5532 management and control, data processing and data uploading. Keyboard and LCD are the input and output devices of the whole system, and they are the main ways of human-computer interaction. The data display program can draw polarizability and resistivity curves on LCD. Data upload is completed through USB and network. The following focuses on data acquisition and data processing procedures.

Design of (1)DWZ-6A Multifunctional Electrical Instrument Data Acquisition Program

The design of data acquisition program is mainly to control CS5532 to achieve high-precision data acquisition. This part includes the underlying drivers and applications of CS5532 under uClinux system. When writing the driver of CS5532, the program is written according to the chip technical documents, the chip working sequence and the requirements of the ip instrument itself. The control of CS5532 mainly includes sampling rate control and A/D gain control. CS5532 underlying driver mainly includes simulating SPI, CS5532 initialization, filling the file_operations structure of character device driver in uClinux system, timed interrupt, external interrupt, etc. The driver of the character device in uClinux system is mainly to write sub-functions to fill in the fields of file_operations. According to the actual demand of IP instruments, the CS5532 device driver only needs the open, ioctl, release and read functions in the file_operations structure. The operation of CS5532 application program on the underlying driver includes the opening of device files, the reading and writing of device files and the closing of device files. The main function calls are as follows:

Geophysical methods, techniques and instruments for water exploration

(2) The data processing program design of DWZ-6A multifunctional electric measuring instrument.

DWZ-6A Multifunctional Electrical Method Instrument has designed the acquisition modes of various devices (step, sounding, combined profile, etc.). ) In the geophysical prospecting electrical method, the common acquisition parameters of various devices are built in, and the geophysical prospecting parameters such as natural potential, primary potential, power supply current, apparent resistivity, apparent polarizability and half-life are intelligently processed. The data processing program deeply processes the data collected by CS5532 according to geophysical methods, thus calculating the above-mentioned earth. Among them, apparent resistivity and apparent polarizability are important parameters in IP instruments, and the calculation formulas of apparent resistivity ρS and apparent polarizability ηS are as follows:

Geophysical methods, techniques and instruments for water exploration

Please refer to Chapter 2 for the principle and formula of main parameters of DWZ-6A multifunctional electrical instrument.

The signal collected by DWZ-6A multifunctional electric measuring instrument contains certain noise. Although analog circuits have been filtered and denoised, the performance of analog filters is limited. In order to improve the quality of geophysical parameters in IP instrument, a software digital filter, 50Hz band-stop FIR filter, is added to the data processing program.

In order to improve exploration efficiency, suppress interference signals in field measurement and optimize the measurement accuracy of apparent polarizability, positive and negative alternating rectangular pulse current is used for data acquisition. The secondary potential difference and total field potential difference measured by positive power supply and negative power supply are △V2p, △V2n, △Vp and △Vn, respectively. Therefore, the formula for calculating the apparent polarizability used by DWZ-6A multifunctional electrical instrument is as follows:

Geophysical methods, techniques and instruments for water exploration

The above secondary potential difference is the result of a certain delay time after the transmission circuit is powered off, so the secondary potential difference has a certain relationship with the delay time. Different models of multi-functional appliances have different measurement results due to different delay times. DWZ-6A multifunctional electrical appliance has five kinds of power-off delay time, which can handle five kinds of apparent polarizability, and at the same time, it can manually input the delay time to get the apparent polarizability parameters of the expected power-off delay.

Four. Function and technical index of DWZ-6A multifunctional electrical method instrument

DWZ-6A multifunctional electrical prospecting instrument is a new type of intelligent multifunctional electrical prospecting instrument developed to meet the demand of water prospecting. That is, it can be used to find water, geothermal energy and ore, and can also be used for geological exploration in engineering geology, environmental geology and energy geology. DWZ-6A multifunctional electrical prospecting instrument is equipped with a low-power transmitter, and can also be equipped with a high-power transmitter above 10kW, which works in the form of short wires and is used for deep exploration. External high-density multi-electrode converter can be used for high-density electrical survey with low emission power, and is used for hydrogeological exploration, engineering geological exploration and environmental geological exploration. Equipped with a high-power transmitter above 10kW, it can carry out high-power or ultra-high-power high-density electrical survey, and carry out deep and rapid prospecting. At present, no second company in the world has developed an ultra-high power and high density electrical measurement system (generally only a few hundred watts). DWZ-6A multifunctional resistivity instrument has the characteristics of multi-function, good performance, many parameters, high power, high technical index and wide application.

The parameters measured and calculated by DWZ-6A multifunctional electrical apparatus include apparent resistivity, apparent polarizability, half-life, attenuation, comprehensive parameters, deviation, excitation ratio, relative attenuation time and charging rate.

Main technical indexes of DWZ-6A multifunctional electrical method instrument:

Voltage measuring range: 10V

Voltage measurement accuracy: 0.2%

Current measuring range: 10A

Accuracy of current measurement: 0.2%

Input impedance: greater than 60MΩ

Self-compensation range: 2000mV

50Hz suppression: greater than 80dB

Maximum power supply voltage:1200 v v.

Maximum power supply current: 10A

Power supply time: 1 ~ 99s optional.

Interface: USB, RS232

Working temperature:-10℃ ~+55℃

Working humidity:

In the second quarter eh-4 electromagnetic instrument

1. Method and principle of EH-4 electromagnetic imaging system

Eh-4 electromagnetic imaging system belongs to the magnetotelluric exploration system which combines controllable source and natural source. The natural background field source (MT) is used to image the deep structure. In the shallow structure, the portable low-power transmitter emits artificial electromagnetic signals of 500 Hz ~ 100 kHz to make up for the shortage of natural signals, so as to obtain high-resolution imaging.

If the earth is regarded as a horizontal medium and the magnetotelluric field is a plane electromagnetic wave vertically projected into the ground, then the orthogonal electromagnetic field components can be observed on the ground as Ex and HY. Hx, Ey. By measuring orthogonal electric and magnetic field components, the resistivity value of the medium can be determined. Its calculation formula is:

Geophysical methods, techniques and instruments for water exploration

Where: f is the frequency in hertz; ρ is the resistivity, and the unit is Ω m. Because the underground medium is inhomogeneous, the calculated ρ value is called the apparent resistivity value. The detection depth is theoretically the skin depth, and the calculation formula is

Geophysical methods, techniques and instruments for water exploration

δ is the skin depth. The above formula shows that the penetration depth of electromagnetic wave increases with the increase of resistivity and the decrease of frequency.

Second, eh-4 instrument system

Eh-4 system mainly consists of three parts: transmitting, receiving and data processing. See 6-2- 1 for the schematic diagram of the system and figure 6-2-2 for the layout of field work.

Fig. 6-2- 1EH-4 system working principle diagram

Figure 6-2-2 eh-4 Site Work Layout

(1) receiving part

It is mainly composed of host, preamplifier (AFE), magnetic sensor, electrode with buffer and its accessories.

1) host is the center of the whole system, which is mainly used for file management, data acquisition and data processing. It uses IBM portable computer, 8MB memory, 8 10MB hard disk, 8-bit analog-to-digital conversion 18 bit, 32-bit floating-point digital processing, LCD VGA display and working temperature of 0 ~ 50℃.

2) The pre-amplifier filters and amplifies the collected electromagnetic field signal and transmits it to the host through the transmission line. Set up four channels (two channels and two tracks) with the built-in rechargeable battery.

3) The magnetic sensor is mainly used to collect magnetic field information, and the observation frequency response range is: standard configuration (BF- 1m type),10 Hz ~100 kHz; Low frequency configuration (BF-2m type), 0. 1 Hz ~ 1 kHz.

4) The electrode is mainly used to receive electrical information. The standard configuration is BE- 16 type buffer electric sensor, 16m cable and titanium steel electrode; The low frequency configuration is BE-50 buffer electric sensor, 50m cable and CuSO4 nonpolar electrode.

(2) 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, which is novel in concept and one of the unique features of the system. The transmitting frequency of the transmitter itself is 500 Hz ~ 100 kHz, which matches the impedance of the transmitting antenna. Using different transmitting antennas, their transmitting frequencies are different. The standard antenna is adopted, and the transmission frequency is 1 ~ 64 kHz. The antenna is equipped with low frequency, and the transmission frequency is 500 Hz ~ 32 kHz.

The positioning of transmitter is very important. Because the data processing software of EH-4 system is based on the premise that the field source is far away from the measuring point (that is, the far field area). If the transmitter is too close or too far away, it will have a great impact on the test results, and even produce false anomalies, so the transmitter of the system can move quickly and conveniently, which is one of the unique features of the system. In principle, the distance between the transmitter and the receiver is 3 ~ 4 times that of the deepest target detected by the controllable source. Theoretically, the transmitting-receiving distance (R) should be three times the "skin depth" δ at the lowest working frequency, that is

Geophysical methods, techniques and instruments for water exploration

Where: r is the receiving and sending distance; δ is the skin depth; ρ is the average resistivity of the earth; F is the lowest operating frequency.

(3) data collection and data processing

1. data acquisition

The data acquisition mode of the system is time domain acquisition, and then Fourier transform is carried out to convert it into frequency domain signals, that is, four electromagnetic signals (two paths and two paths) are collected in time domain, and Fourier transform is carried out to convert them into power spectra of real and imaginary parts of electromagnetic signals, and apparent resistivity, phase difference and correlation coefficient are calculated through frequency spectrum.

For the standard configuration, the whole sampling frequency band is divided into three bands:10 Hz ~1khz (1band); 300 Hz ~ 3 kHz (4 frequency bands); 1.5 ~ 99 kHz (7 frequency bands). The number of times of superposition can be set artificially for each segment. According to the signal quality, the stacking times are determined, and the signal quality is good and the stacking times are few. The sampling of each frequency point is divided into three sections. The sampling time of the launch site is 20ms, and there are 4096 sampling points. Each segment is Fourier transformed, and the final sampling frequency is 60. For the low frequency configuration, the sampling method is similar to the standard configuration, but the sampling time is correspondingly longer. The whole frequency band is divided into two parts (50hz ~1khz; 0. 1Hz~75Hz)。

2. Output file

No matter what configuration the system has, there are four output files, which are standard configuration: @ file, Y file, X file and Z file; Low frequency configuration; @ l, v, u, w. The @ (or @ l) file is a survey information file. It mainly includes the working frequency and initial gear number, the position of transmitter and receiver, the length of dipole distance in X and Y directions and the internal gain setting in 16. Y (or V) file is a binary time series file. The x (or u) file is a cross-power spectrum file, and each line consists of 19 columns, each column is 1 1 characters, and the units are H-NT, E-V/KM and F-Hz. The z (or w) file is a text impedance file. Each frequency point consists of 12 lines, with 8 characters in each column. This file is the final processing file. The main contents include frequency, scalar apparent resistivity, phase and correlation in X and Y directions, and eight impedance elements with real and imaginary parts.

3. Data processing

There are two kinds of data processing: real-time processing and subsequent processing. Real-time processing: according to the apparent resistivity, phase, correlation and amplitude curves given by each measuring point, the data quality is analyzed in real time. For some unreliable data that can be eliminated from the curve, continue to measure, or the data quality of the whole curve is too poor, take measures to implement repeated measurement. After the continuous observation of the whole survey line is completed, EMAP method (which can effectively eliminate the static effect) can be used to give the gray map of the quasi-two-dimensional inversion interpretation results. Post-processing is the work done indoors after the field work, which generally includes two contents: one is to adjust the correlation coefficient and filter coefficient of field data on the host computer or to reprocess the time series data (Y or V files) one by one. Minimize the influencing factors, highlight useful anomalies, and 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 the PC for further quantitative interpretation and two-dimensional inversion processing, and color mapping is carried out.

Three. Main parameters of EH-4 electromagnetic imaging system

Working principle: natural and artificial magnetotelluric current tensor field

Standard frequency range: 10 Hz ~ 100 khz

Transmitter: TxIM2 transmitter with vertical antenna coil.

Frequency: 500 Hz ~ 70 kHz

Pulse: 400 Amp-m2

Antenna size: two 4m2 vertical cross coils.

Power supply: 12V, 60Ah battery

Electrodes: 4 Be-26 effective high-frequency dipoles with buffers, 4 SSE stainless steel electrodes and 26m cable.

Magnetic rod probe: two BF- 1m magnetic induction rods (10hz ~ 100khz) and 10m cables.

Analog terminal: 1 AFE-EH-4 analog signal regulator, which is used to transmit the signal of the electrode to the acquisition unit.

Bandwidth of a pair of magnetic rods: DC-96 kHz

Processor: 32-bit floating point

Display: LCD VGA

Printer: Built-in 4-inch (1 1 cm) printer.

Power supply: 12V, 40Ah

Working temperature: 0 ~ 50℃

Instrument box: light, strong and waterproof.

Options:

Configure StrataViewTM

Low frequency MT bar: 0. 1 ~ 1 kHz

Electrodes: 4 Be-50 effective high-frequency dipoles with buffers and 50m cable.

High power antenna: frequency range: 300 ~ 35 kHz

Pulse: 6000 Amp-m2

Antenna size: 2 45m vertical cross coils.

Data acquisition unit:

Number of channels: 4 channels (2 electrical channels, 2 magnetic channels)

Built-in computer: IBM is compatible with 80486CPU8MbRAM and floppy disk.

Hard disk: 1.2G or above

A/D conversion: 18 bits