High Precision Synchronous Acquisition System for the Current Data in Marine Electromagnetic Transmitter

Marine electromagnetic transmitter is one of the key devices for marine electromagnetic exploration, the large current transmitted by the device as well as the data collected by the receiver would undergo process and invert calculation to master the shallow resistivity structure under the seabed. The high precision synchronous acquisition system in this literature is the critical step in this procedure. LPC2368 is adopted in this system as main control unit, and GPS time service is adopted to realize the synchronization with the data from receiver in the acquisition procedure. Temperature compensated crystal oscillator, CPLD time synchronization and frequency division technology as well as time synchronization error query method are adopted in the circuit to ensure the time precision would be up to microsecond, then save the data as well as relevant absolute time to U disk with the CH375 port convert module in real time manner, with the purpose to ensure the completely storage of the current data of marine electromagnetic transmitter. It is proved in the marine experiment that this system has satisfied the designed requirement. Keywords—marine electromagnetic transmitter; synchronous acquisition; high precision; real time storage