Design And Development Of Electromagnetic Ultrasonic Testing Instrument Based On FPGA

As a new Nondestructive Testing technology,Electromagnetic Ultrasonic testing has been paid more and more attention,because of whose unique advantages and high efficiency.The paper will describe the research and development of EMAT.At first,analysis the basic principle of EMAT.Then utilize a large number of mathematical formulas to calculate corresponding.Introduce several kinds of ultrasonic wave in solid medium and propagation velocity.At last,derive completed mathematical equation of the EMAT system.According to detection principle of EMAT,analysis probe structure and design the detector probe.In the EMAT system,probe is made of bias magnetic field and coil.The bias magnetic field has three choice,like AC electromagnet,DC electromagnet and permanent magnet.All of them have different advantage and disadvantage,comparing and analyzing them.Finally,the permanent magnet is chosen to provide the bias magnetic field.The coil of EMAT probe is different from the common coil.Due to the particularity of the coil of the probe,a new method of coil need to be developed.The project adopts new plan to design the coil,which is simple and whose parameters are accurate and which can meet the design requirements of EMAT coil.Complete the design of the hardware system of EMAT instrument which based on FPGA.The system includes hardware system of excitation source,receive signal conditioning circuit and digital system on FPGA chip.The design of excitation source system is based on the principle of DDS and adopt FPGA technology to produce sine pulsing signal.Then sine pulsing signal input power amplifier circuit.Next the output pulsing signal can meet the requirement of EMAT.The receiving signal conditioning system is mainly to receive return signal.And return signal input the amplifier,band-pass filter,A/D conversion circuit.At last,return signal is converted into digital signal,which is acquired by FPGA,through on-chip processing and sent to the display port.In this paper,the design of EMAT instrument adopts the FPGA chip as core device.Based that,complete the design of hardware circuit and software and the design of test probe.