Study On Flow Velocity And Volume Measuring Technique And Unit Based On MEMS Thermal Flow Sensor

China is a big country of production and consumption of agricultural products. China is alos a big country and export of agricultural products. With the improvement of China’s rapid economic development and people’s living standards, people’s demand for agricultural products has not only limited to local seasonal. People are more concerned towards cross-regional, cross-time agricultural. People also have higher requirements for the quality of agricultural products, In many of these products are perishable agricultural commodities. However, Compared to the huge circulation of agricultural products, China’s cold chain logistics industry has not developed. Especially refrigerated truck ownership and performance are far behind the developed countries. In developed countries, more than 80% of the perishable agricultural use refrigerated transportation. In China, the figure is only about 20%. The lack of cold chain transportation for perishable agricultural products caused the greatly waste. Many of the frefigerated trucks only have temperature measuring devices. There is no means for measuring air flow inside. Airflow inside the truck is not controllable. This has resulted in uneven distribution of temperature and humidity inside. For some strict in storage environment of transportation of the high-grade agricultural truck is difficult to do. This paper discusses the current flow velocity and volume measuring technologies. To measure the airflow inside refrigerated trucks, this paper presents a special designed MEMS-based thermal flow velocity and volume measuring unit.The measuring unit is designed for flow velocity and volume measurement of the frefigerator outlet. In this paper, MEMS based flow velocity and volume measuring unit is made up of MEMS thermal flow sensor, CTA control circuit, A/D conversion circuit, MCU based interface circuit, water proved device package. The MEMS thermal flow sensor and CTA control circuit is used to measure the air velocity, the wind velocity is converted into a voltage signal. The A/D conversion circuit is used to convert the voltage signal into digital signals. MCU based interface circuit is used to calculate the flow velocity and volume. It sends the data to the controller of the refrigerator. A Water proved device package seales the unit, protects its internal electronic components. A CFD simulation and a environmental endurance test are conducted. MEMS hot flow sensor based flow volecity and volume measuring unit worked normally. The unit can adopt the special environment in refrigerated trucks, mearure the flow velocity and volume precisely. The implementation of the unit has a positive effect on controlling the environment inside refrigerated trucks.