The Study Of The On-Board Instrument For Exhaust Gas Measurement

Exhaust gas emission of the gasoline engines is the main source which causes air pollution．Moreover, the emission is interrelated to the combustion of gasoline engines．In order to reduce the amount of the emission, it is necessary to study the relationship between ignition parameters and the emission. Therefore, it is important to design an on-board instrument which make real-time measurement of the emission continuously．In this thesis,after studied the principle of gasoline engine and the mechanism of harmful elements in the emission, the author proposed the design of the on-board instrument. Sample equipment of the traditional analysis instrument is too large to be inconvient to test on-board. According to conditions of the requiement of the high temperature of exhaust gas, complex of chemical components and real-time performance, the author chose electric-chemistry gas sensor, which has the characteristics of low price, high efficiency and identification. Super chopper-stabilized amplifier ICL7650 is adopted in the preamplifier circuit. Double integrate A/D convertor and the A/D convertor in the CPU are adopted in the circuit. The equipment is mainly consisted of a single-chip computer 80c196KB, a little LCD displayer, a real-time clock chip, and a serial EEPROM. Such equipment owns the advantages of convient for observing and operating, It not only has the function of the measurement of exhaust gas, but also can record the surpass exhaust gas. On the basis of the completed hardware circuit, the author made the programme of the control module, and debugged the oxygen channel. The author has also taken measures in both hardware and software against the interference according to the interference source and its transmission ways in the automobile. The on-board instrument make it possible to study the relationship between ignition parameters and exhaust gas emission. It can also monitor the emission related system and components(e.g. catalyzer) in order to keep the the amount of exhaust gas under the permitted limit during the whole life cycle of the automobile. In addition, through the continous inspecting of the exhaust gas of automobiles, the drivers canrepair their automobiles when they find the surpass gas. And the real-time record of the surpass gas can be used as the evidence of the traffic authority for the punishment of the drivers.