DESIGN OF FLAW DETECTION HARDWARE SYSTEM IN ELECTROMAGNETIC ULTRASONIC INSPECTION SYSTEM

As a non-contact flaw detection technology, electromagnetic ultrasonic has a wide application prospect, especially suitable for harsh working conditions. However, due to the low energy conversion efficiency of the sensing elements of the electromagnetic ultrasonic testing equipment, the large electromagnetic interference of the transmitting circuit, and the attenuation problem of the ultrasonic propagation in the tested piece, the echo signal is low and often submerged in the noise, which cannot correctly reflect the acoustic reflection characteristics of the tested piece. The hardware flaw detection circuit is designed in this paper,which can effectively improve the signal strength, reduce the introduction of noise and suppress the propagation attenuation. The gain compensation module is composed of AD9762, AD603and field programmable gate array(FPGA), which mainly aims at the attenuation of ultrasonic propagation. The ultrasonic testing experiment on the aluminum standard specimen shows that the circuit magnification of the device can reach 110000, the signal-to-noise ratio is high, and the detection of weak signal reflected by defected is realized; The signal gain compensation is realized, and the echo signal error caused by ultrasonic propagation attenuation is improved, which has good engineering application value.