Research On Data Transmission Technology In Seismic And Electrical Distributed Acquisition Stations

With the continuous exploration of deep geophysical exploration,it is difficult to meet the actual needs of China's exploration work by relying on a single geophysical exploration method.Multi-method joint exploration has become the current hot research direction.Seismic and electrical methods are currently widely used geophysical exploration methods.It is of great significance to study seismic and electrical methods for distributed acquisition stations.Among them,the data transmission technology in the collection station is the focus and difficulty of the current research.The seismic and electrical distributed acquisition stations designed in this paper are divided into main control core board and analog acquisition board from hardware.The main control core board is designed with FPGA as control chip.Two analog-to-digital converters are designed on the analog acquisition board as a data conversion channel for seismic and electrical methods,respectively.The distributed acquisition station is connected in series via a 4-core line.The 4-core line is divided into two pairs of twisted pairs.It has the dual functions of data transmission and power supply.In addition to send and receive full-duplex data,power is also provided to each acquisition station.The FPGA control chip allocates two pairs of LVDS differential pins to interface with the 4-core line through a network transformer.In addition to transferring data and extracting power,the network transformer also has electrical isolation.Through the Quartus II development environment,VHDL hardware description language is used to realize the data transmission technology in distributed acquisition stations.Data encoding and decoding modules are designed in each acquisition station.The data transmission of the acquisition station adopts Manchester encoding,and simultaneous parallel-to-serial conversion of the data is performed.The main clock of the encoding module is 32.768 MHz,so the data transmission rate of the large-line is 16.384 Mbps.The decoding module extracts the synchronous clock on the transmission line using an oversampling technique with 8 times the data transfer rate,and decodes the serial data according to the clock,and forms 8-bit parallel data by shift conversion.The transmission of data frame on the acquisition chain is divided into two directions: synchronous and asynchronous.The transmission of data frame on the acquisition chain is divided into two directions: synchronous and asynchronous.In the synchronous transmission direction,synchronous acquisition commands need to be sent and data acquisition and data frame transmission tasks are performed.The asynchronous transmission direction only needs to transfer data frame.Through the time difference of the data frame reaching the acquisition station in both directions,and with the help of the time of the data frame staying in each acquisition station,each acquisition station makes a corresponding response after receiving the synchronization acquisition command according to its position in the acquisition chain.The time delay can realize the synchronous acquisition of each acquisition station.After the indoor and outdoor test,the seismic and electrical distributed acquisition station designed in this paper works normally and the data transmission is stable and reliable.