| The electronic function module is the base of the mechanism and electronic products. The quality of whole instrument is determined by each component on PCB. Now automatic testing system on PCB is mostly produced by European or American. It is more expensive and far beyond the affordability of small and medium electronic enterprises in China. In order to strengthen their competitive power, the paper develops the testing system for PCB using In-circuit Test (ICT) which is easy to use, has low price and suits to them.This paper discusses the principles and characteristics of various PCB testing technologies in detail. According to users which the case faces and their requirements of PCB test, in-circuit test is used in the testing system for PCB. Based on virtual instrument technology, it can test analog electronic components, combinational logic circuits and functional modules that are consisted of on PCB. The system included ICT instrument, logical analysis unit, signal generators, high-speed data acquisition, multi-path channel scanners and nails-bed. ICT instrument used different testing method for different object and carried out the segregation between tested object and other components on tested PCB by potential isolating ways, and the precision of tested object was improved by using self-adaptive testing method. Logical analysis unit can test usual combinational logic circuits using reverse driver technology. Signal generator can produce double usual waveform such as sine wave, square wave, oblique wave, triangle wave etc. Data acquisition can collect four signals simultaneously and communicate with PC by USB interface. Multi-channels scanner was designed by mini-relay matrix with better scalability. Nails-bed used new type fixture, which not only has good contact performance but also does no harm to contact point.Practical testing data indicates that the system can implement the automatic testing for usual PCB function module, and achieves the desired requirements. |
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