The Reaserch Of Transient Electromagnetic Signal Acquisiton And Processing

Transient Electromagnetic Method is a kind of geophysical methods and basedon the principle of electromagnetic induction. It’s used to predict the undergroundmineral and referred to as TEM. Transient Electromagnetic Method is not onlysimple in operation, and the information obtained by this method is large and highprecision. Therefore, this method has been widely used, especially in the mineralexploration application. This method uses the receiver to complete the transientelectromagnetic signal acquisition. The collected transient electromagnetic signalcontains geological information associated with the ore. To analys is the data, thedistribution of underground ore body profile can be explained.Through this thesis, we researched the principle and characteristics of transientelectromagnetic method and analyzed in detail the acquisition method of transientelectromagnetic signal and noise. And proposed to use both a digital multi-pointaverage method and the sampling integral method in transient electromagneticsignal acquisition system. In this way, the system can use the advantage of digitalmulti-point average method to avoid using high-resolution AD chip and avoid theearly signal of saturation. also use the capabilities of the sampling integral methodto submerge weak signal extraction in the noise. The system only requires anintegrator and can avoid complexity circuit compared to use a plurality of samplingintegrator. In this thesis, the system used FPGA as a system master chip, while thesampling channel selection, the choice of the integration time constant, etc. areswitched through the analog switch. Sampling integral circuit selected the lineargate integrating circuit and the communication circuit design used the CypressCY7C68013A chip to complete the USB interface circuit design.Finally, the hardware circuit acquisition system has done functional testing andgive the test results, this paper also analyzed the test results. The test results showthat the sampling integrator circuit has a great advantage in weak signal extractionthat drowned in the noise. The test results also show that the digital multi-pointaverage method and the sampling integral method both used in transientelectromagnetic signal acquisition system is feasible.