Study On Gasoline Octane Value Measurement System Based On Capacitance Sensor

With the great development of industry and economy, the number of automobiles has been significantly growing and the gasoline markets have been becoming more and more on-limits. However, gasoline of poor quality is always existed and gasoline qualities are disparate in market. Gasoline of poor quality can be seriously harmful to automobile combustion engine and aggravate the pollution degree of tail gas. In order to identify and better manage gasoline, gasoline should be identified during producing and delivering.Octane value is defined as one of the most important standards to measure the main elements and quality of gasoline. At present, there are many ways to measure the gasoline Octane value, however, some obvious disadvantages are unsolved such as high cost, complex operation, bad real-time and low accuracy, which can not satisfy actual requirements. As capacitance sensors are of many significantly advantages, a Gasoline Octane value detect system is proposed in this article, which is based on capacitance sensor and the analysis of many gasoline Octane value detecting methods. The system contains the power modules, sensor circuit, temperature acquisition module as well as MCU software and hardware design. According to a priori knowledge, there is a linear relationship between gasoline Octane value and dielectric constant, if the linear relationship is deduced from a great number of gasoline with pre-known Octane value, the Octane value of gasoline with pre-known Octane value can be measured according to the deduced linear relationship.In addition, there is always water obtained in gasoline and temperature has a great effect on dielectric constant of water, so this effect should be considered as the environment temperature is changing at all times. There are two methods mentioned in this article to measure capacitance, and capacitance/voltage changing module was applied in the final system according to experiments.The experiment consists of two steps. Firstly, a great number of gasoline with pre-known Octane value were measured to get the linear relationship between gasoline Octane value and dielectric constant. Then, three kinds of gasoline with Octane value of 90#,93# and 97# were measured under the same temperature and different temperature respectively. The absolute of gasoline can be less than 1.4 and the relative error can be less than 2% from the experiment data. The system proposed in this article is of many advantages such as low cost, good stability and better real-time which can be widely applied in gasoline identification, pipeline delivering and gasoline producing. A similar system based on capacitance sensor can be used in the domain of food detecting, which shows great development prospects.