Seismic Data Acquisition, Gps Timing System

GPS (Global Positioning System) is developed by America for the purpose of high precision navigation and position, a kind of Global Passivity Wireless Satellite System. It began to be used in 1993 in deed, which consists of three parts: GPS satellites, the control system on ground and GPS receiver. At present, GPS is abroad used in aviation, spaceflight, earth survey, electronic communication, electrical power fault detection and so on.GPS can provide not only position service, but also timing service for user through high stability atom clock of GPS satellite. At present, most of Earthquake Data Acquition System (EDAS) obtain timing service from GPS timing transmission and short-time keeping provided by local clock, the combine timing service owns characteristic of high precision timing, high stability and high cost performance, etc. based on the previous method of GPS timing transmission, this paper introduces IRIG-A code into the timing system as transmission timing code, which improves the reliability and validity during time transmission, being of important significance in seismic array observation.The GPS timing system owns the function of decoding information of GPS, encoding IRIG-A and decoding IRIG-A. The interface of 1PPS signal is provided in Transmit end and receive end, which can be used to synchronize external clock for high precision. The GPS timing system uses LEA-4H OEM board produced byμ-blox corporation which is located in Switzerland, and LPC2132 ARM microcontroller produced by PHILIPS corporation. It is of excellent performance, low power consumption, small volume and high cost performance.Chapter 1 introduces the research background and significance of the paper;Chapter 2 introduces development and application fields of GPS; Chapter 3 introduces IRIG code and its application in time synchronization; Chapter 4 and 5 contain the important content, introducing the design and implementation of GPS timing system, such as verifying GPS information, encoding and decoding IRIG-A, and how to implementing through hardware and software; Chapter 6 analyzes performance indicators of system and explains some points being worth for improvement; chapter 7 summarizes the paper. The GPS timing system could mark time base for collection data of EDAS and provide precision time synchronization signal. According to practical demand, the system could also realize easily some expansion peripheral interface and peripheral display circuit, being of high value in use.