| The Transient Electromagnetic Methods (TEM) was used in mineral exploration and geological research as a physical detection method in the beginning, and then it was used in municipal engineering and coal mine detection. It is applies the research of the defective metal pipes and the electromagnetic characteristics which are excited by TEM, and a new non-destructive testing methods based on the transient electromagnetic field. is proposed as a result, this testing method can detect certain equipments or components that the traditional methods cannot achieve, meeting the special needs of process engineering applications.Based on the theoretical study and analysis, the launch systems and receiving systems based on transient electromagnetic detection theory is designed. The transmitting part of the new system has strong emission signal, high demand of the waveform of the transmitter circuit and turn-off time. For the receiving part, the transient signals should have dynamic range, a high voltage of pre-signal, and decay severely of the late-signal. Additionally, the new system has high demands on acquisition system, which needs to be collected by floating-point amplification.The electrical part of transient electromagnetic testing logging system is the emphasis in this research, Circuit of transmitting and receiving of the electromagnetic system are designed, including the optical isolation circuit, the driver circuit of MOSFET, the bridge power converter circuit in the transmit circuit; and the pre-circuit, the low pass filtering circuit, the sub-amplification circuit, the float amplified circuit, the AD sampling circuit in the receive circuit.In this thesis, the timing control based on the FPGA is researched, and A variety of wave can be transmitted in the transient electromagnetic nondestructive testing has been achieved, Besides, The programmable magnification can be controlled by using FPGA, and it is tested and verified by some electrical testing experiment. |
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