EMAT Detecting System Design For Pipeline Defect Based On VI

The defect detection of pipeline is an important means to assure the safety inproduction. Compared with the traditional piezoelectric ultrasonic testing technology, theelectromagnetic ultrasonic testing technology has the advantages of non-contactdetection,dispense with couplant,high speed, easy to implement online automaticdetection, suitable for high temperature environment,and so on.Now EMAT is widelyused and researched.On the other hand,the emergence of virtual instrument technologyhas subverted the traditional instrument design concept.With the necessary hardwaremodule,we can achieve more powerful functions than traditional instruments through thegraphical programming platform LabVIEW. Programs of virtual instrument are simpleand intuitive, the user can flexibly modify the function of the instrument according toneeds.Based on the above background, the topic is the design of the EMAT pipenondestructive testing system based on virtual instrument technology. Design thenecessary electromagnetic ultrasonic receiving circuit,and process ultrasonic signal usingthe powerful data processing ability of LabVIEW platform.Based on the analysis of the EMAT, the paper designed combined EMAT transducerto realize2D locating of pipeline defect. Designed hardware circuits including theAT89C52single chip microcomputer control circuit, ultrasonic emitting circuit, ultrasonicreceiving circuit, data acquisition circuit, power circuit, etc. Single chip microcomputercontrols the launch of the pulse signal by C language programming,then the pulse signalis sent to the ultrasonic transmission circuit to generate ultrasonic signal. Due to the lowefficiency of EMAT, designed two-stage amplifier circuit of preamplifier and controllablegain amplifier for receiving signal to amplify. Data acquisition circuit includes detectioncircuit and A/D conversion circuit. Single chip microcomputer communicates with theLabVIEW platform by the serial port agreement. Designed human-computer interaction interface of the EMAT pipe nondestructive testing system based on LabVIEW, selectedthe wavelet denoising algorithm in ultrasonic signal denoising, constructed waveletdenoising subVI using LabVIEW,verified the effectiveness of wavelet denoisingalgorithm through simulation.