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A distortion tester of geophone based on FPGA

Distortion is an important performance of geophone and it can effect the accuracy of the data obtaining in seismic exploration directly. In this paper, a distortion tester based on FPGA (Field Programmable Gate Array) has been designed. On the base of the dynamic and equivalent circuit models of geophone and the analysis of windows, the measurement is exciting the geophone by a sine current signal, transforming the windowed response sequence by FFT (Fast Fourier Transform) and calculating the distortion of response. The DDS(Direct Digital Synthesis) to generate excitation signal and FFT are realized on the FPGA. Experiments to test the distortion of GP903/4A-10Hz geophone have been done and the results show that the measurement is sample and test precision is high. The application of FPGA also makes the tester low cost, low power, small size and it is easy to be upgraded.