| Environment has great influence to electric contact, because there are a lot of corrosion products in the air, such as corrosive gases, dust particle, etc. The component is very easily eroded by those factors, so that the contact interface is not metal-to-metal. Corrosion films will grow between contact interface, such as sulfuret and other corrosion products. In high frequency transmission system, when contact spots eroded , it will lead to impedance non-matching, this is an important reason of signal attenuation. Among most research to system transmission impedance, contact spot is often regarded as an ignoring cell, or only consider the influence from contact resistance, thus, we should do more research on impedance character of contact under high frequency signal.The paper has done some theoretical analysis about the impedance module of contact spot. The contact impedance include three parts: contact resistance, contact capacitance, contact inductance. The main factors affecting the impedance of contact spot include signal frequency, the topographic and the component of the corrosion products. Then the paper make use of scanning microwave microscope, do some impedance test on contact spot to analyze how these factors influence the impedance of them from a microcosmic angle. The test results indicate that, the more serious contact spot eroded, the contact impedance will be more bigger. Contact resistance will increase with the signal frequency increasing, Contact capacitance will decrease with the signal frequency increasing, Compared with large contact resistance, the influence of contact inductance on contact impedance could be ignored. Besides, through contact spot impedance test on different corrosion products, it could get the impact extent of different corrosion products on contact spot impedance character. The test result indicate that nitric acid stream influence the contact spot impedance much more than sulfur dioxide.
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