Design And Implementation Of New Eddy Current Testing Excitation Signal Source

Eddy current testing as one of the five regular non-destructive testing methods, has itsunique advantages, has been widely used in machinery, electric power, oil, aviation,chemical and metallurgy industries. Eddy current testing system consists of the followingthree parts: the magnetic field measure devices, data sampling system and excitation source.As an effect of eddy current testing system performance is one of key components ofexcitation signal source, the performance will affect the stability of eddy current testingsystem. With the continuous development of technology of eddy current testing, eddycurrent testing system for the excitation signal source of the increasingly high demand, thetraditional excitation signal source has been unable to meet the needs of the eddy currenttesting. As the fastest growing frequency synthesis technology recently, direct digitalfrequency synthesis (DDS) have fast converting speed, excellent temperature and agingstability, frequency conversion constant phase ability, as well as small and reliable, usingDDS technology to design excitation signal source can meet the requirements of eddycurrent testing.Based on the analysis of the basic principle of DDS, the spectrum structure andspurious source, introduces several repressing stray methods, put forward to MCU andCPLD is the key device of the excitation signal source system hardware architecture. Thedesign of C51language to write MCU program, mainly to complete the control wordscalculation, the management of serial interface and man-machine interface; using hardwaredescription language and principle diagram input methods to write CPLD program, mainlyto complete phase accumulator, address latch and other logic function; using c++languageto write PC program, mainly to complete waveform sampling and serial interfacecommunication function. In addition, the system of man-machine interface is used to realizeby the touch screen, which is easy to use, rapid response, space saving, convenientcommunication etc.At last, the paper introduces the system each module hardware and software debuggingresults, the system can realize the arbitrary waveforms output, and the results of thedebugging and error analysis, and introduces the debugging process of the problemsencountered and solutions. From the experimental results we can see that the design is feasible, and can meet the requirements of excitation signal in the eddy current testing.