In recent years, the measurement and controlment of the tiny gas flow have been gained widely attention in some emerging areas, such as biological, medical, aerospace and so on. In order to study the characteristics of the tiny gas flow meter, the tiny gas flow calibrator based on the principle of the Symmetric plunger is designed, which the flow range of the calibrator is from 5mL/h to 1000mL/h. The structure and the working principle are introduced, the uncertainty's Sources and classification of the tiny gas flow calibrator are analyzed, the uncertainty components are analyzed and calculated, The expanded uncertainty of the device is less than 0.126%, which conforms to the design requirements of the device, and it have reached the advanced level at home and abroad. Finally, according to the experiment of the soap film flowmeter, The expanded uncertainty of calibration for the soap film flowmeter is less than 0.77%.

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