CN108828671A - High-precision degree passes formula seismic prospecting data collecting system - Google Patents

Abstract

The invention relates to a high-precision digital transmission type seismic exploration data acquisition system, in order to solve the problem of high cost and high power consumption when the acquisition system collects seismic data in the ocean, it includes a main control computer, an acquisition unit, a data packet, a hydrophone and a power supply The main control computer completes the processing, waveform display and storage of seismic data; the acquisition unit realizes the data acquisition, storage and communication functions, and the data acquisition circuit of the acquisition unit adopts high-precision analog-to-digital converter ADS1282 and fully integrated digital data suitable for seismic testing. Analog converter DAC1282, Field Programmable Gate Array FPGA is the control center of the seismic acquisition station; when the system is working, the main power station sends data frame packets containing control commands and synchronization information to the acquisition unit, and the data acquisition unit will collect the data according to Sequentially fill in the data frame packet and continue to transmit it backwards. After receiving the data frame packet, the power station performs data processing and compression and then continues to transmit it to the subsequent data acquisition unit. When collecting seismic data in the ocean, it has the advantages of low cost, high precision and low power consumption.

Description

High-precision digital transmission seismic exploration data acquisition system

technical field

The invention relates to a seismic exploration data acquisition system for seismic data acquisition in the ocean, in particular to a high-precision digital transmission type seismic exploration data acquisition system.

Background technique

With the rapid development of the national economy, the demand for marine resources is increasing day by day. The shortage of marine resources has become the bottleneck of the sustainable development of the national economy, and the foreign dependence of some oceans has reached the edge of danger. At present, most of the domestic and foreign developments are non-marine mineral resources within 1000m, and non-seismic exploration methods are used for exploration, such as electrical and electromagnetic methods, which play an important role in oil and gas and coal exploration, of which oil and gas exploration accounts for about About 90% of the total exploration volume. There are some successful cases of using seismic exploration technology to detect marine resources, but there are still many difficulties to be overcome, mainly because the conditions of most marine resources are complex, which is very unfavorable for the acquisition and processing of marine data. Marine seismic exploration technology is in its infancy both at home and abroad. Internationally, countries such as Canada and Australia are trying to adopt petroleum seismic technology in marine exploration. The domestic Chinese Academy of Sciences and the Academy of Geological Sciences are respectively trying petroleum exploration technology and engineering seismic technology in marine exploration. But neither achieved good results. The reason is that due to the particularity of ocean bottom conditions, exploration has the characteristics of large exploration depth and high resolution, and conventional seismic exploration technology is not suitable for ocean exploration. Therefore, the design of high-precision digital transmission seismic data acquisition system is imminent.

At present, there is no comprehensive seismic exploration system for marine exploration at home and abroad. Most of them use instruments used in oil and coal exploration. However, these instruments are large and heavy, and are not suitable for seismic exploration of complex seabeds. Compared with oil, natural gas and coal, the exploration expenditure of the ocean is generally small, so it is of great significance to develop a low-cost high-precision marine seismic exploration system.

Contents of the invention

The object of the present invention is to overcome the above-mentioned defects of the prior art, and provide a low-cost, high-precision, and low-power high-precision digital transmission type seismic exploration data acquisition system when seismic data acquisition is performed in the ocean.

In order to achieve the above object, the high-precision digital transmission type seismic exploration data acquisition system of the present invention is a seismic exploration data acquisition system for seismic data acquisition in the ocean, mainly including a main control computer, an acquisition unit, a data packet, a hydrophone and a power supply; The main control computer mainly completes the seismic data processing, waveform display and storage; the acquisition unit mainly realizes the data acquisition, storage and communication functions. Integrated digital-to-analog converter DAC1282, field programmable gate array FPGA is the control center of the seismic acquisition station; the hydrophone is mainly used to sense the seismic wave signal; the seismic wave information is collected, amplified and filtered by the acquisition station of the acquisition unit, and then The digitized seismic signal is sent to the central recording system of the main control computer and recorded; when the system is working, the main power station sends a data frame packet containing control commands and synchronization information to the acquisition unit, and the data acquisition unit fills the collected data in order After receiving the data frame packet, the power station performs data processing and compression and then transmits it to the subsequent data acquisition unit. The acquisition of seismic data is an important technical link in seismic exploration. The technical index of the acquisition unit is crucial to the quality of marine data acquisition, and the index of the data acquisition unit depends mostly on the selection of the analog-to-digital conversion unit. Therefore, The present invention focuses on the design of the analog-to-digital conversion unit, and then adopts the FPGA-based digital logic design method and PowerPC 405 to process the seismic data, successfully reducing the hardware scale of the acquisition station circuit design in terms of hardware, reducing the cost and Power consumption, and then carry out remote transmission through LVDS data transmission mode, so as to transmit the collected data to the PC host. The data acquisition circuit adopts the high-precision analog-to-digital converter ADS1282 produced by Texas Instruments and the fully integrated digital-to-analog converter DAC1282 suitable for seismic testing. Because ADS1282 integrates analog electronic switches, programmable amplifiers and digital filters, it greatly simplifies the complexity of circuit design and reduces power consumption. The invention has new breakthroughs in resolution and power consumption. It has the advantages of low cost, high precision and low power consumption when seismic data acquisition is performed in the ocean.

As an optimization, the acquisition unit is a data acquisition circuit based on the high-precision analog-to-digital converter ADS1282 and the fully integrated digital-to-analog converter DAC1282; its main function is to receive the I/O control logic and acquisition of the main control circuit of the field programmable gate array FPGA command, to perform analog-to-digital conversion on the electrical signal responded by the hydrophone, and the obtained digital signal is sent to the FPGA main controller for calculation and processing; the field programmable gate array FPGA is used as the control center of the seismic acquisition station, and its main function is to provide data acquisition The circuit sends control instructions and provides relevant chip pin control logic levels to set the sampling rate and sampling length required for data acquisition, set the gain of the preamplifier and switch the working mode and input channel, while receiving, analyzing and forwarding from the power station The incoming data frame. After the data stream is processed by the field programmable gate array FPGA chip, Manchester encoding is performed inside the chip, and the encoded data is converted into a differential signal by the LVDS chip, and then sent to the cable after being isolated by the network transformer, and then transmitted to the next collection station . The power supply circuit of the acquisition station is embedded in the data acquisition board and the field programmable gate array FPGA main control board, realizing a power supply mode similar to PoE, taking power from the transmission line and performing a series of voltage conversions, providing power for the data acquisition circuit board And the field programmable gate array FPGA main control circuit board provides a stable DC power supply. Among them, it is converted into a differential signal through the LVDS chip, and then sent to the cable after being isolated by the network transformer.

As an optimization, the preamplifier AMP, 24-bit Σ-Δ analog-to-digital converter and digital filter are used as the data acquisition part, and the FPGA and LVDS transmission chip are used as the data processing and transmission part.

As an optimization, the digital logic design method based on Field Programmable Gate Array FPGA and PowerPC405 are used to process seismic data.

As an optimization, the data packet uses a series of ultra-low power consumption voltage conversion circuits according to the power supply requirements of each chip on the main control circuit and data acquisition circuit. That is, the design of the power supply circuit is the key to realize the low power consumption of the data packet. According to the power supply requirements of each chip on the main control circuit and data acquisition circuit, the data package has designed a series of ultra-low power consumption voltage conversion circuits. Data packets may also be referred to as digital packets.

As an optimization, the pre-filter circuit is used in the data acquisition unit to process the analog signal at the front end, and the excitation source switching circuit between the actual acquisition channel and the DAC test channel is used. That is, in the data acquisition unit, in order to achieve a good acquisition effect, a pre-filter circuit is designed for front-end processing of the analog signal. In order to facilitate the testing of various performance indicators of the data acquisition circuit, the excitation of the actual acquisition channel and the DAC test channel is designed. source switching circuit.

As an optimization, the main control module of the acquisition unit uses a field programmable gate array FPGA chip 3C5T144C5N and PowerPC405. The main control module adopts field programmable gate array (FPGA) chip 3C5T144C5N and PowerPC 405, which not only reduces the scale and complexity of hardware circuit design, but also improves the reliability of the system.

As an optimization, the data transmission circuit uses a simulated LVDS transceiver to realize synchronous data transmission. The data transmission circuit adopts LVDS to realize synchronous data transmission, thereby realizing multi-channel synchronous data acquisition through the link.

As an optimization, the simulated LVDS transceiver is that after the data stream is processed by the field programmable gate array FPGA chip, Manchester encoding is performed inside the chip, and the encoded data is converted into a differential signal by the LVDS chip, and then sent to the cable after being isolated by the network transformer. , transmitted to the interior of the next collection station. Among them, it is converted into a differential signal through the LVDS chip, and then sent to the cable after being isolated by the network transformer.

As an optimization, the pre-filtering and channel switching circuits of the acquisition unit are GEOH and GEOL respectively connected to the positive and negative poles of the hydrophone output; a pair of BAV199 switching diodes limit the input voltage between -2.5V and +2.5V; resistors R13, R14, R17, R18 and capacitor C13 form a differential filter to remove high-frequency normal mode components from the input signal; capacitors C12, C14 and resistors R14 and R18 form a common-mode filter to remove high-frequency common-mode components from the input signal ; Resistors R15 and R16 set the middle bias level of the input signal to the ground level, and at the same time form a bias current return with the input terminal of ADS1282; AOUT2+ and AOUT2- are connected to the analog input terminal of ADS1282.

The technical scheme adopted by the present invention to solve its technical problems is: the power circuit in the data acquisition system is designed with low power consumption; the data acquisition unit adopts the high-precision analog-to-digital converter ADS1282 produced by Texas Instruments and applicable DAC1282 is a fully integrated digital-to-analog converter for seismic testing. Because ADS1282 integrates analog electronic switches, programmable amplifiers and digital filters, it greatly simplifies the complexity of circuit design and reduces power consumption; FPGA-based The digital logic design method and PowerPC 405 process seismic data to improve the speed and precision of data processing. In terms of hardware, the hardware scale of the circuit design of the data acquisition station has been successfully reduced, and the cost and power consumption have been reduced. Then, the LVDS data transmission method is used for remote transmission, so that the collected data is transmitted to the PC host. The system has the characteristics of high precision, low power consumption, self-detection, and low cost, which provides many conveniences for ocean exploration and saves a lot of manpower and material resources.

The working principle of the present invention: when the system is working, the main power station sends a data frame packet containing control commands and synchronization information to the acquisition unit, and the data acquisition unit fills the collected data into the data frame packet in order and continues to transmit it backwards. After receiving the data frame packet, the power station performs data processing and compression and then transmits it to the subsequent data acquisition unit. The main control computer decodes and decodes the data and records them. Considering that the internal space of the seismic acquisition station is very limited, a cascade design is adopted in the hardware circuit structure. The seismic acquisition station as a whole is composed of a data acquisition circuit board and an FPGA main control circuit board. The I/O interface between them is through 2 A 26-pin double-row pin with a 2.54mm pitch is used for vertical docking.

Beneficial effects of the present invention: the invention has the advantages of high precision, low power consumption, low cost, portability, etc., and is suitable for seismic exploration of the ocean. The data acquisition circuit uses the ADS1282 and DAC1282 chips developed by TI as the core of the acquisition station, improving the The resolution and dynamic range of the collected data; the FPGA-based digital logic design method reduces the hardware scale of the circuit design and verifies its correctness through experiments; the low power consumption design of the power module in the system and the selection of the ADS1282 chip not only reduce the The number of batteries used, and the reduction of manpower, material and financial resources, are also of great benefit to marine exploration.

Description of drawings

Fig. 1 is the principle block diagram of the seismic data acquisition circuit based on ADS1282 and DAC1282 in the high-precision digital transmission type seismic exploration data acquisition system of the present invention; V isolation circuit schematic diagram; Figure 3 is the 3.3V to 2.V and 1.2V circuit schematic diagram of the power circuit; Figure 4 is the 3.3V to +2.5VA circuit schematic diagram of the power circuit; Figure 5 is the 3.3V to +2.5VA circuit schematic diagram of the power circuit; -2.5VA circuit schematic diagram; Figure 6 is a 2.5V reference voltage circuit schematic diagram of the power supply circuit.

Fig. 7 is a schematic diagram of the pre-filtering and channel switching circuit of the high-precision digital transmission type seismic exploration data acquisition system of the present invention; Fig. 8 is a fully integrated digital-to-analog converter DAC1282 circuit of the high-precision digital transmission type seismic exploration data acquisition system of the present invention Schematic diagram; Fig. 9 is a circuit schematic diagram of high-precision analog-to-digital converter ADS1282 in the high-precision digital transmission type seismic exploration data acquisition system of the present invention; Fig. 10 is a field programmable gate array in the high-precision digital transmission type seismic exploration data acquisition system of the present invention FPGA main control circuit structural block diagram; Fig. 11 is the simulation LVDS transceiver circuit schematic diagram in the high-precision digital transmission type seismic exploration data acquisition system of the present invention; Fig. 12 is the simulation LVDS transceiver in the high-precision digital transmission type seismic exploration data acquisition system of the present invention LVDS interface isolation circuit diagram of the device.

Detailed ways

Below in conjunction with accompanying drawing, the present invention will be further described: the high-precision digital transmission type seismic exploration data acquisition system of the present invention is the seismic exploration data acquisition system that carries out seismic data acquisition in ocean, mainly comprises main control computer, acquisition unit, data packet and hydrophone Among them, the main control computer mainly completes the seismic data processing, waveform display and storage; the acquisition unit mainly realizes the data acquisition, storage and communication functions, and the data acquisition circuit of the acquisition unit adopts high-precision analog-to-digital converter ADS1282 and applicable The fully integrated digital-to-analog converter DAC1282 for seismic testing, the field programmable gate array FPGA is the control center of the seismic acquisition station; the hydrophone is mainly used to sense seismic wave signals; the seismic wave information is collected and amplified by the acquisition station of the acquisition unit , filtering, and then send the digitized seismic signal to the central recording system of the main control computer for recording; when the system is working, the main power station sends a data frame packet containing control commands and synchronization information to the acquisition unit, and the data acquisition unit will collect the The data is filled into the data frame packet in order and transmitted backwards. After receiving the data frame packet, the power station performs data processing and compression and then transmits it to the subsequent data acquisition unit. The acquisition of seismic data is an important technical link in seismic exploration. The technical index of the acquisition unit is crucial to the quality of marine data acquisition, and the index of the data acquisition unit depends mostly on the selection of the analog-to-digital conversion unit. Therefore, The present invention focuses on the design of the analog-to-digital conversion unit, and then adopts the FPGA-based digital logic design method and PowerPC 405 to process the seismic data, successfully reducing the hardware scale of the acquisition station circuit design in terms of hardware, reducing the cost and Power consumption, and then carry out remote transmission through LVDS data transmission mode, so as to transmit the collected data to the PC host. The data acquisition circuit adopts the high-precision analog-to-digital converter ADS1282 produced by Texas Instruments and the fully integrated digital-to-analog converter DAC1282 suitable for seismic testing. Because ADS1282 integrates analog electronic switches, programmable amplifiers and digital filters, it greatly simplifies the complexity of circuit design and reduces power consumption. The invention has new breakthroughs in resolution and power consumption. It has the advantages of low cost, high precision and low power consumption when seismic data acquisition is performed in the ocean.

Specifically, the acquisition unit is a data acquisition circuit based on the high-precision analog-to-digital converter ADS1282 and the fully integrated digital-to-analog converter DAC1282; its main function is to receive the I/O control logic and acquisition commands of the field programmable gate array FPGA main control circuit , carry out analog-to-digital conversion on the electrical signal responded by the hydrophone, and the obtained digital signal is sent to the FPGA main controller for calculation and processing; the field programmable gate array FPGA is used as the control center of the seismic acquisition station, and its main function is to provide data to the data acquisition circuit Send control instructions and provide relevant chip pin control logic levels to set the sampling rate and sampling length required for data acquisition, set the gain of the preamplifier and switch the working mode and input channel, and receive, analyze and forward the data transmitted from the power station at the same time. After the data stream is processed by the field programmable gate array FPGA chip, Manchester encoding is performed inside the chip, and the encoded data is converted into a differential signal by the LVDS chip, and then sent to the cable after being isolated by the network transformer, and then transmitted to Inside the next acquisition station; the power supply circuit of the acquisition station is embedded in the data acquisition board and the field programmable gate array FPGA main control board, realizing a power supply mode similar to PoE, taking power from the transmission line and performing a series of voltage conversions , to provide a stable DC power supply for the data acquisition circuit board and the field programmable gate array FPGA main control circuit board. Among them, it is converted into a differential signal through the LVDS chip, and then sent to the cable after being isolated by the network transformer.

Specifically, the preamplifier AMP, 24-bit Σ-Δ analog-to-digital converter and digital filter are used as the data acquisition part, and the FPGA and LVDS transmission chip are used as the data processing and transmission part.

Specifically, the digital logic design method based on Field Programmable Gate Array FPGA and PowerPC405 are used to process seismic data.

Specifically, the data packet adopts a series of ultra-low power consumption voltage conversion circuits according to the power supply requirements of each chip on the main control circuit and data acquisition circuit. That is, the design of the power supply circuit is the key to realize the low power consumption of the data packet. According to the power supply requirements of each chip on the main control circuit and data acquisition circuit, the data package has designed a series of ultra-low power consumption voltage conversion circuits. Data packets may also be referred to as digital packets.

Specifically, the pre-filter circuit is used in the data acquisition unit to process the analog signal at the front end, and the excitation source switching circuit between the actual acquisition channel and the DAC test channel is adopted. That is, in the data acquisition unit, in order to achieve a good acquisition effect, a pre-filter circuit is designed for front-end processing of the analog signal. In order to facilitate the testing of various performance indicators of the data acquisition circuit, the excitation of the actual acquisition channel and the DAC test channel is designed. source switching circuit.

Specifically, the main control module of the acquisition unit adopts field programmable gate array FPGA chip 3C5T144C5N and PowerPC405. The main control module adopts field programmable gate array (FPGA) chip 3C5T144C5N and PowerPC 405, which not only reduces the scale and complexity of hardware circuit design, but also improves the reliability of the system.

Specifically, the data transmission circuit uses a simulated LVDS transceiver to realize synchronous data transmission. The data transmission circuit adopts LVDS to realize synchronous data transmission, thereby realizing multi-channel synchronous data acquisition through the link. The simulated LVDS transceiver is a field programmable gate array FPGA chip that processes the data stream and performs Manchester encoding inside the chip. The encoded data is converted into a differential signal by the LVDS chip, and then sent to the cable after being isolated by the network transformer and transmitted to Inside the next collection station. Among them, it is converted into a differential signal through the LVDS chip, and then sent to the cable after being isolated by the network transformer.

Specifically, the pre-filtering and channel switching circuits of the acquisition unit are GEOH and GEOL respectively connected to the positive and negative electrodes of the hydrophone output; a pair of BAV199 switching diodes limit the input voltage between -2.5V and +2.5V; resistors R13 and R14 , R17, R18 and capacitor C13 form a differential filter to remove high-frequency normal mode components from the input signal; capacitors C12, C14 and resistors R14 and R18 form a common-mode filter to remove high-frequency common-mode components from the input signal; Resistors R15 and R16 set the intermediate bias level of the input signal to the ground level, and at the same time form a bias current return with the input terminal of ADS1282; AOUT2+ and AOUT2- are connected to the analog input terminal of ADS1282.

The present invention will be further described below with reference to accompanying drawing:

Fig. 1 is a schematic diagram of the data acquisition circuit based on ADS1282 and DAC1282 in the high-precision digital transmission type seismic exploration data acquisition system of the present invention. Its main function is to receive the I/O control logic and acquisition commands of the field programmable gate array FPGA main control circuit, perform analog-to-digital conversion on the electrical signal responded by the hydrophone, and transmit the obtained digital signal to the FPGA main controller for calculation and processing. FPGA is the control center of the seismic acquisition station. Its main function is to send control instructions to the data acquisition circuit and provide related chip pin control logic levels to set the sampling rate and sampling length required for data acquisition, and to set the preamplifier gain and switching. Working mode and input channel, while receiving, analyzing and forwarding data frames from the power station. After the data stream is processed by the FPGA chip, Manchester encoding is performed inside the chip, and the encoded data is converted into a differential signal by the LVDS chip SN65MLVDS200, and then sent to the cable after being isolated by the network transformer 540042 WE-MIDCOM NL1548, and then transmitted to the next collection station internal. The power supply circuit of the acquisition station is embedded in the data acquisition board and FPGA main control board, realizing a power supply mode similar to PoE, taking power from the transmission line and performing a series of voltage conversions, providing power for the data acquisition circuit board and FPGA main control circuit The board provides a stable DC power supply.

2-6 are schematic diagrams of the design of the power supply circuit in the high-precision digital transmission seismic exploration data acquisition system of the present invention. The power supply circuit is the key to realizing low power consumption of the distributed seismic acquisition station. According to the power supply requirements of each chip on the FPGA main control circuit and data acquisition circuit, the distributed seismic acquisition station designed a series of micro-power consumption voltage conversion circuits. The digital voltage of the FPGA main control circuit and data acquisition circuit is 3.3V, and a 48V to +3.3V DC isolated power supply needs to be designed. The FPGA chip also needs to supply +1.2V (or +1.1V) core voltage and +2.5V configuration voltage, so +3.3V to +1.2V (or +1.1V) and +2.5V circuits are designed. In the data acquisition circuit, the power supply voltage of the analog circuit part is +2.5VA and -2.5VA, +2.5VA can be converted by +3.3V, and -2.5VA needs to be converted from +3.3V to -3.3V and then to -2.5V VA. Chips such as ADS1282 and DAC1282 need a high-precision reference voltage +VREF and -VREF, and the voltage difference between the two is 2.5V. In addition, the power ground wire is also divided into common reference ground GND, digital power ground DGND and analog power ground AGND in the circuit, and the three are finally connected by magnetic beads to achieve single-point common ground.

Fig. 7 is a schematic diagram of the pre-filtering and channel switching circuit in the high-precision digital transmission seismic exploration data acquisition system of the present invention. In the figure, GEOH and GEOL are respectively connected to the positive and negative poles of the hydrophone output. A pair of BAV199 switching diodes limits the input voltage to -2.5V to +2.5V. Resistors R13, R14, R17, R18 and capacitor C13 form a differential filter to remove high frequency normal mode content from the input signal. Capacitors C12, C14 and resistors R14, R18 form a common-mode filter to remove high-frequency common-mode components from the input signal. Resistors R15 and R16 set the middle bias level of the input signal to the ground level, and at the same time form a bias current loop with the input terminal of the ADS1282. AOUT2+ and AOUT2- are connected to the analog input of ADS1282.

Fig. 8 is a schematic circuit diagram of the high-precision analog-to-digital converter DAC1282 in the high-precision digital transmission seismic exploration data acquisition system of the present invention. It operates on a bipolar power supply with ±2.5V for analog and 3.3V for digital. The input terminals SWINP and SWINN of the transfer switch are respectively connected to the output terminals DACOUT+ and DACOUT- of the DAC, and the output terminals SWOUTP and SWOUTN are respectively connected to the input terminals GEOH and GEOL of the analog pre-circuit. Therefore, the output from the DAC can be realized by controlling the switching of the switch. Pulse, THD and Common Mode Rejection Ratio tests from port to hydrophone input. In addition, DACOUT+ and DACOUT- are also connected to the second input channel of ADS1282, which can realize the channel test from the output end of DAC to the input end of ADS1282. The main clock input of DAC1282 is 4.096MHz, which is generated by an external active crystal oscillator. In order to synchronize with the clock of ADS1282, both share the same clock source. FPGA configures DAC1282 through the SPI interface composed of CS, SCLK, DIN, and DOUT.

Fig. 9 is a schematic circuit diagram of a fully integrated digital-to-analog converter ADS1282 in the high-precision digital transmission type seismic exploration data acquisition system of the present invention. It uses a bipolar power supply, the analog power supply is ±2.5V, the digital power supply is 3.3V, and the external reference voltage is +2.5V. The input clock is a 4.096MHz clock source shared with the DAC1282. The first differential input channel AOUT1+/- is connected to the DAC1282 differential output channel DACOUT+/-, and the second differential input channel AOUT2+/- is connected to the output terminal of the pre-circuit. FPGA controls ADS1282 through the SPI interface composed of SCLK, MISO, MOSI and DRDY. ADS1282 also provides an external synchronous signal input port SYNC and signal overshoot flag output port MFLAG.

Fig. 10 is a structural block diagram of the field programmable gate array FPGA main control circuit in the high-precision digital transmission seismic exploration data acquisition system of the present invention. Two LVDS receivers and two LVDS transmitters are designed in the main control circuit to realize double-ended data transmission between the acquisition station and external equipment. Since the design uses the LVDS interface located at the top and bottom I/O blocks of the FPGA, it only supports emulation of the LVDS interface type. Therefore, LVDS as a transmitter needs to be equipped with a specific external resistor network as shown in Figure 11, where the resistance of RS is 170Ω, and the resistance of RP is 120Ω, while the LVDS as a receiver needs to be connected in parallel with an external matching resistor of 100Ω at the input . In addition, in order to avoid the influence of other signals on LVDS, avoid allocating other GPIO resources in the I/O block where the LVDS interface is located during design.

Fig. 11 is a circuit diagram of a simulated LVDS transceiver in the high-precision digital transmission seismic exploration data acquisition system of the present invention. After the data stream is processed by the FPGA chip, Manchester encoding is performed inside the chip, and the encoded data is converted into a differential signal by the LVDS chip SN65MLVDS200, and then sent to the cable after being isolated by the network transformer 540042 WE-MIDCOM NL1548, and then transmitted to the next collection station internal.

Fig. 12 is the LVDS interface isolation circuit in the high-precision digital transmission seismic exploration data acquisition system of the present invention. The LVDS transceiver signal of the FPGA and the line signal are isolated and coupled through the isolation circuit shown in Figure 12. Since the seismic acquisition station adopts a double-ended transceiver transmission structure, two network isolation transformers are required. The isolation transformer adopts HR601680E produced by Hanren Company. Its primary coil is connected to a four-core large wire, and ±24V power can be extracted from the center tap CT and CMT. The secondary coil is connected to the LVDS transceiver differential line pair. 1. An optional 1.2V bias voltage circuit is configured on the TCT to stabilize LVDS signal transmission.

The technical scheme adopted by the present invention to solve its technical problems is: the power circuit in the data acquisition system is designed with low power consumption; the data acquisition unit adopts the high-precision analog-to-digital converter ADS1282 produced by Texas Instruments and applicable DAC1282 is a fully integrated digital-to-analog converter for seismic testing. Because ADS1282 integrates analog electronic switches, programmable amplifiers and digital filters, it greatly simplifies the complexity of circuit design and reduces power consumption; FPGA-based The digital logic design method and PowerPC 405 process seismic data to improve the speed and precision of data processing. In terms of hardware, the hardware scale of the circuit design of the data acquisition station has been successfully reduced, and the cost and power consumption have been reduced. Then, the LVDS data transmission method is used for remote transmission, so that the collected data is transmitted to the PC host. The system has the characteristics of high precision, low power consumption, self-detection, and low cost, which provides many conveniences for ocean exploration and saves a lot of manpower and material resources.

The working principle of the present invention: when the system is working, the main power station sends a data frame packet containing control commands and synchronization information to the acquisition unit, and the data acquisition unit fills the collected data into the data frame packet in order and continues to transmit it backwards. After receiving the data frame packet, the power station performs data processing and compression and then transmits it to the subsequent data acquisition unit. The main control computer decodes and decodes the data and records them. Considering that the internal space of the seismic acquisition station is very limited, a cascade design is adopted in the hardware circuit structure. The seismic acquisition station as a whole is composed of a data acquisition circuit board and an FPGA main control circuit board. The I/O interface between them is through 2 A 26-pin double-row pin with a 2.54mm pitch is used for vertical docking.

Beneficial effects of the present invention: the invention has the advantages of high precision, low power consumption, low cost, portability, etc., and is suitable for seismic exploration of the ocean. The data acquisition circuit uses the ADS1282 and DAC1282 chips developed by TI as the core of the acquisition station, improving the The resolution and dynamic range of the collected data; the FPGA-based digital logic design method reduces the hardware scale of the circuit design and verifies its correctness through experiments; the low power consumption design of the power module in the system and the selection of the ADS1282 chip not only reduce the The number of batteries used, and the reduction of manpower, material and financial resources, are also of great benefit to marine exploration.

Claims (10)

1. It is to carry out the seismic prospecting of earthquake data acquisition in ocean 1. a kind of high-precision degree passes formula seismic prospecting data collecting system Data collection system, it is characterised in that mainly include main control computer, acquisition unit, data packet and hydrophone and power supply；Wherein, Main control computer mainly completes the processing of seismic data, waveform is shown and stores；Acquisition unit mainly realize data acquisition, The data acquisition circuit of storage and communication function, acquisition unit using high-precision adc ADS1282 and is suitable for earthquake The fully integrated digital analog converter DAC1282 of test, on-site programmable gate array FPGA is the control axis at earthquake-capturing station；Water is listened Device is mainly used to sense seismic signal；Seismic wave information is to be acquired, amplified by the acquisition station of acquisition unit, filtered, so Digitized seismic signal is sent into afterwards in the central recording unit of main control computer and is recorded；When system works, main power source It stands and sends the data frame packet comprising control command and synchronizing information to acquisition unit, data acquisition unit presses collected data Sequence is packed into data frame packet and continues to transmit backward, and power station carries out data processing and pressure after receiving data frame packet Subsequent resume of contracting gives subsequent data acquisition unit.
2. 2. system according to claim 1, it is characterised in that acquisition unit be based on high-precision adc ADS1282 with The data acquisition circuit of fully integrated digital analog converter DAC1282；Its major function is to receive on-site programmable gate array FPGA The I/O control logic and acquisition of governor circuit carry out analog-to-digital conversion to the electric signal of hydrophone response, obtained number letter It number sends FPGA master controller to and carries out operation and processing；In control of the on-site programmable gate array FPGA as earthquake-capturing station Pivot, major function is to send control instruction to data acquisition circuit and provide related chip pin control logic level, with setting Sample rate, sampling length needed for data acquisition, are arranged preamplification gain and switching working mode and input channel, while receiving, The data frame that analysis and forwarding are transmitted from power station.
3. 3. system according to claim 1, it is characterised in that preposition amplification AMP, 24 Sigma-delta ADC's sum numbers

   Word filter is as part of data acquisition, and FPGA and LVDS transmission chip are as data processing and hop.
4. 4. system according to claim 1, it is characterised in that use the Digital Logic based on on-site programmable gate array FPGA Design method and PowerPC405 handle seismic data.
5. 5. system according to claim 1, it is characterised in that data packet is according to core each on governor circuit and data acquisition circuit A series of power reguirements of piece, using super low-power consumption voltage conversion circuits.
6. 6. system according to claim 1, it is characterised in that believed using pre-filter circuit simulation in data acquisition unit Number carry out front-end processing, and using actual acquisition channel and DAC TCH test channel driving source switching circuit.
7. 7. system according to claim 1, it is characterised in that the main control module of acquisition unit uses field-programmable gate array Column fpga chip 3C5T144C5N and PowerPC405.
8. 8. system according to claim 1, it is characterised in that data transmission circuit is realized using emulation LVDS transceiver and synchronized Number passes.
9. 9. system according to claim 8, it is characterised in that emulation LVDS transceiver is data flow by field programmable gate After the processing of array fpga chip, portion carries out Manchester's code in the chip, and the data sent out after coding are turned by LVDS chip It is changed to differential signal, cable is sent into after being isolated using network transformer, is transmitted to inside next acquisition station.
10. 10. system according to claim 1, it is characterised in that the pre-filtering of acquisition unit and channel switching circuit are GEOH

    Connect hydrophone output positive and negative anodes respectively with GEOL；A pair of of BAV199 switching diode by input voltage be limited in -2.5V to+ Between 2.5V；Resistance R13, R14, R17, R18 and capacitor C13 constitute difference filter and remove high frequency normal mode from input signal Formula ingredient；Capacitor C12, C14 and resistance R14, R18 constitute common-mode filter, and high frequency common mode ingredient is removed from input signal；Electricity Resistance R15, R16 set the intermediate bias level of input signal as ground level, while the composition bias current with the input terminal of ADS1282 It returns；AOUT2+ and AOUT2- connects the analog input end of ADS1282.