The Research Of Petroleum Products Closed Cup Flash Point Tester

Petroleum products closed cup flash point (PPCFP), which reflects the quality and safety of petroleum products, is one of the necessary testing indexs. Compareed with international testers, there are still a lot of necessary improvements for domestic PPCFP testers in many aspects such as precision, stability, efficiency and operation interface.According to the two test standards for the determination of PPCFP, GB/T 261issued by P.R.C. and ASTM D93 issued by American Society of Testing Materials, an automatic PPCFP testing system with high precision, high reliability and convenient operation is designed. A core solution with MSP430F169 as control unit and EPM240 as coprocessor for interfaces and functions is designed. 16 bit A/D converter AD7705 withΣ-Δtechnology is used to develop the precision. An internal extended bus based on RS 232 is designed to enhance the expansibility of the instrument. At same time, LCD controller, touch screen controller and flash disck reader are successfully connected on the bus.While Pt100 temperature sensor is used to replace liquid thermometer in automatic testing instruments of petroleum products, there are discriminations on dynamic characteristic which bring errors to measuring. So, dynamic characteristic of Pt100 temperature sensor must be compensated based on the liquid thermometer. This paper analyses the mathematical models of sheathed Pt100 sensor and GB1 mercury thermometer, and introduces 3rd order model to describe the dynamic characteristic of sheathed Pt100 sensor for the first time. Their transfer functions are evaluated, via step response experiments, assisted with simulation using MATLAB software. A compensation algorithm based on transfer functions is presented, which can be used to make the former approach the latter on dynamic characteristic. In practice, the algorithm can get better compensation effect than the traditional method which compensates with a selected static temperature curve, and also can be used in temperature measurement systems in which dynamic characteristic of sensors are definitely required.The debugging and running of the PPCFP tester indicate that it has the characteristics of simpler structure, lower cost, easier operation, higher reliability and friendly interface. It brings the working efficiency and the accuracy, meets the need of production and possesses good value of promotion.