Analogue Circuit Fault Diagnosis Utilizing Noise Measurements And Analysis

In the recent years, more and more people had paid close attention to fault diagnostic approach and orientation to analogous circuit, and it's a big difficult problem for expert in the aspect of design and application. The traditional approaches to fault location of IC modules are performed only if the faults of the circuits are those hard faults, such as open-circuit, short-circuit, or parameter changes, etc. Along with application and development of large-scale integrated circuit, people must have the aid of computer to find out the faults of the circuits in order to maintain component and equipment. Fault diagnostic approach to analogous circuit had became a amazing subject in large-scale integrated circuit, especially, Those hidden defects of circuit components cannot be easily discovered and may form early or sudden circuit faults. Though survey the noise and theory value computation of electric circuit output to judge whether electric circuit does break down. This article not only proposed the failure detection plan, but also emphatically discuss the measuring technique of diagnosis system, and haddeveloped the electric circuit output noise power spectrum measurement system, this set of system core is the high performance digital signal processor (DSP) which use the output noise of FFT power spectrum metering circuit. All above has provided the new theory basis and measuring technique for the fault diagnostic approach to analogous circuit, and hopefully develops a set of highly effective detection facilities.The electric circuit is composed by the massive integrated orginalpart and the discrete component, therefore there are many hidden defect in the electric circuit. These hidden defect is particular refer to the fault that be reduced by the level in the manufacture of semiconductor and the rule of the device when it working or by the long work time. Therefore the noise sources of the integrated component are too more to be measured and simulated one by one. The article makes use of two ports module of the circuit method, so that the noise analysis of the integrate component and the system became easier. In the next, the article discuss the way to resolve the problem in calculating the complicated electronic circuit output noise and raises theautomation degree of calculation further. For the measurement of output noise, it focus on the measurement of electric output noise spectrum. In order to reduce the error, this article use the method based on FFT power spectrum cyclic graph law to measure the system output noise spectrum.In order to get the measure value better, the hardware platform must have the low noise characteristic of the hardware system and anti-interference measure. The system adopt a low noise pre-amplifier, its background noise is very small and can suitable for the low noise-measuring occasion. Because the system use the FFT power spectrum to achieve the measurement of electric output noise, the measurement cycle could be more longer, so we would use a high performance digital signal processor to solve. Then we cooperate with other peripheral devices, such as CPLD, AD to finish the job of measurement. Moreover we should consider the combinability in the hardware platform, the platform essential component is the programmable part, may the on-line rewriting procedure complete the different function, so other signal processingplatform also may use this hardware platform.This article research work divides into two parts: first part is to use noise analysis method diagnosis analogous circuit defect theory and the realization method. In this part, firstly introduced electronic noise knowledge and compound circuit noise analysis theory, in the basis of these proposed the noise analysis of electronic defect diagnosis, and carried on the analysis to its feasibility. The second part is the noise measurement system development. This part firstly analysis the examinational characteristics of weak noise signal and determine the detect method, introduced noise detect system hardware principle, composition and the design debugging of this topic in detail, finally carried on the simulation diagnosis experiment.This topic include (1) On the basis of existing knowledge, proposed the integrity noise analysis principle base on the method and Realization of analog system fault diagnostic.(2) propose one kind Pspice analysis program which take for computer circuit theory output noise power spectrum methodsupplement existing Pspice computation noise method.(3) It has Analyzed and compared the existing method of signal measurement, and has analyzed the error performance in the method of Noise Cross-spectrum Measurement . It offered the theoretical direction for the choice of the method.(4)For develop this kind of hardware platform, this platform may carry on the high-speed digital signal, the hardware platform regards DSP as the core. The adjacent device is including CPLD, AD converter, high-speed memory and 89C51 MCU. (5) carried on the experiments for defect diagnose, the result of experiment is the same to theory result.(6) use this hardware platform in others situations. Operate 4-levels wavelet in this hardware system is proved perfect and stabile.