Coast-down time measuring system based on photoelectric method

Abstract

Coast-down time measuring system can measure the time when speed values of Chassis Dynamometers for Automobile Emissions Testing change from initial velocity to end velocity under different load in a given speed range. This coast-down time will represent characters of Chassis Dynamometers for Automobile Emissions Testing such as Dynamometer inertia weight, constant load coast-down time, variable load coast-down time, Chassis Dynamometers for Automobile Emissions Testing can be calibrated by comparing these coast-down time with theoretical values. Working principle of coast-down time measuring system is a photoelectric sampler of coast-down time measuring system collects speed values information of Chassis Dynamometers for Automobile Emissions Testing. Then, determine speed values through calculation. When the velocity is equal to initial velocity V b value, measuring system starts a timer. When speed reaches end velocity V e value, measuring system stops the timer. So time interval is coast-down time from V b to V e . It is obvious that accuracy of coast-down time measurement lies on whether start and end velocity can be judged accurately and determined quickly, whether accuracy of timing can be admitted, and lies on how long these can be done. Coast-down time measuring system with photoelectric sampler proposed in this paper involves all the above factors, as well as improves measurement accuracy of coast-down time.