Study On Suppression Technologies Of Electromagnetic Compatibility Of Taximeter

Electromagnetic Compatibility (EMC) is a fast growing area of science and technology.From the practical application point of view,if the EMC problems are not so1ved properly,it will affect the international and domestic business trading,the progress of the society and influence the health of people.The EMC problems have been paid much more attention by all societies and communities in the world due to its complexity and challenging problems.The subject is supported by Science and Technology Committee of Tianjin(05YFSYSF033), and the paper mainly studies around three elements of the electromagnetic disturbance which are disturbance source,coupling path and sensitive equipment, and focuses on radiation disturbance characteristics of measuring apparatus, and illustrates the suppression technologies. The main contents are the following:1. The paper studies the current situation in domestic and foreign and content of EMC. It discusses and analyses the characteristic of disturbance sources and coupling path, and mainly illustrates the characteristic of conductivity coupling,shared impedance coupling,induction coupling and radiation coupling. So it provides theoretical basic for actual problems.2. It analyses the prediction model of EMC, and makes mathematical model applying field method and circuit method for disturbance source,coupling path and sensitive equipment. Then it studies on the mathematical model of common mode voltage and differential model voltage, and visually illustrates the characteristic of electromagnetic radiation field which forms strong radiation to surrounding environment and equipments. It provides theoretical basic and analysis method for actual problems.3. This project gives a deep study for the relationship between field intensity of radiation interference and test distance within a same radiator. This paper analyses the causation of harmonic current emission of electrical equipments in theory. The method and effect of how to reduce emission are illustrated.The inductance's high frequency equivalent circuit model is given,and the parameter analysis method is provided from which the material performance of the ferrite core can be obtained.By testing the insert loss of the inductance with ferrite core,and then can obtain the effective magnetic permeability.4. The Tianjin municipal government in 2006 replaced Taxi-meter with a new generation, the radiated disturbance indicators of domestically Taxi-meter do not meet national standards in the detection of the Government tender. In light of this issue, we studied the issue about the radiation disturbance very deeply, using three measures:①changing the crystal oscillator circuit, increasing grounding, reducing radiation disturbance;②adding filter circuit , suppressing the third harmonic, reducing radiation disturbance; ③the design of anti-interference of taxi cab.Through studying the project and improving the design, we solved the problem that the taxi-meter radiation disturbance indicators do not meet national standards.32,000 taxis were installed non-radiation Taxi-meter in Tianjin.