Development Of 5kW Distributed Electromagnetic Transmitting System

The electric transmitting system is an artificial field source used to transmit an electric shock signal to the earth and other monitoring objects during active source electric survey.According to the different types of emission signals and devices,it can be divided into resistivity method,excited polarization method,AC shock method,charging method,etc.In active source electrical survey,it is necessary to emit different types,frequencies and powers of stimulus signals according to different exploration scenarios.At the same time,for the accuracy of subsequent inversion,transmission and reception need to be strictly synchronized.Due to the complexity of electromagnetic exploration,extremely high requirements are put forward for the development of electromagnetic transmitting system.This thesis aims to develop a 5kW distributed electrical transmission system suitable for electrical exploration,based on the electrical excitation transmission function and electrode switching function,and cooperates with GPS time synchronization module,WIFI communication module,high-speed ADC and micro SD data acquisition and storage equipment,Designed and developed a set of electromagnetic transmitting system suitable for active source electrical prospecting.The development work of the 5kW distributed electromagnetic transmitting system mainly includes hardware and software.The hardware design is mainly divided into transmitter hardware and switcher hardware.The hardware design determines the core functions,technical indicators and supporting auxiliary functions of the transmitting system.Then discuss the implementation of the major functions to achieve the original vision.The hardware finally realized the STM32 single-chip microcomputer and FPGA as the control core of the galvanic transmitter and electrode switcher.The main functional circuits are:1.H-bridge signal inverter circuit;2.ADC data conversion circuit;3.micro SD card data storage circuit;3.Relay control transmitter electrode on-off circuit;4.Ethernet,WiFi and serial port Communication circuit;5.GPS timing circuit.In software,the emphasis is on the implementation of a control program based on ARM control and supplemented by FPGA.Among them are mainly realized:1.Control of the type,frequency and transmission time of the transmitted signal;2.ADC data acquisition control and micro SD card data storage;3.Signal transmission channel switching function;4.Based on TCP communication protocol and host Communication etc.Finally,the functional test of the electromagnetic transmitting system was carried out,and the electromagnetic experiment of the water tank and other electrical experiments were carried out to verify and evaluate the entire transmitting system.The maximum output signal voltage of the transmitter in the 5kW distributed electromagnetic transmission system designed in this paper is 1000V,and the maximum current is 5A.And support three kinds of electric signals in time domain,frequency domain and pseudo-random.The electrode switcher has a withstand voltage of 750V and a maximum current of 5A.It can flexibly and safely switch the signal transmission channel,which is convenient for on-site layout and wiring and improves work efficiency.