Design Of Data Acquisition System Of Lightning Signal

Lightning disaster as a common natural disaster, exist all over the world. Lightning is a threat to construction, electronic products, people and livestock on the ground, therefore it is important to study the genesis and formation of lightning. Collecting the atmospheric electric field data while lightning occurs is an important method of studying the features of lightning. The paper designed an embedded system, which can sense、condition and collect the atmospheric electric field data while lightning occurs. By using this system, the data of transient electric field which occurs with lightning can be collected、stored and transferred, which can provide evidence for studying lightning.Lightning usually is observed in the unattended field environment, sometimes it is observed by multi-station observation. The traditional data acquisition systems are based on PCI and so on, so they get the limitation of a variety of elements, such as large volume、high dissipation、high cost and so on. During the system collects data, the indoor environment must be prepared for every observation point, therefor, the traditional systems can not collect data for a long time in the unattended environment. The electric field produced by lightning is transient electric field. The duration of lightning is very short, usually is about0.2ms, so the data acquisition system should has voltage-trigger and high-speed data sampling rate.The paper designed a data acquisition system based on S3C2440, which can sense、condition and collect the lightning signal. Using a microprocessor to control the system to collect data, transfer data and store data instead of a PC. The data acquisition system has mass storage capacity by using the USB flash disks, and can transfer data to the remote computer in time by network. The system has two channels, one channel is used to collect the slow electric field data, and the other channel is used to collect the fast electric field data. The data of slow electric field can be used to analysis the trend and details of lightning, and the data of fast electric field can be used to study the transient process of lightning. The sampling rate of each channel is12.5MSPS, and the sampling resolution is14bits.The paper finished the system’s hardware design firstly. The traditional design method about software will causes some difficulties, such as long development period, difficult to develop and large work-load. To solve the above problems, the embedded operating system is used as a platform, then programming device drivers and applications on this platform for the data acquisition system.The high-speed pipelined ADC is strict to working time series, its output clock is the same as its input clock, and it also has many clock delays within input and output, so the driver of ADC must be programmed, then the driver can be used to initialize ADC and controlled its working time series. The paper also finished the drivers and applications of USB and network chip, by which to control the system to store and transfer data. At last, the paper designed a interface which for transferring data over network, and designed a observing interface, then the collected data will be shown on the LCD touch screen in curvilinear form, by viewing the interface, the acquisition results can be found out intuitively.