Abstract: In order to measure the micro flow in micro channel precisely and easily, a new measuring method based on the idea of utilizing non-steady flow state to be equivalent to steady flow state used in traditional measurement is proposed. The applicable condition of pressure head for the new measuring method is derived. Based on Lagrange integral principle in fluid dynamics, a mathematic model in form of non-linear differential equation is built and analyzed numerically by using MATLAB software, so the theoretical error of the proposed method is obtained. The numerical results reveal that the difference between measurement result under the non-steady flow state and that under the steady flow state reduces with the decreasing of the ratio of the areas of the micro channel and the tube in upper stream when the pressure loss in the tube is omitted. Then, an apparatus for measuring the micro flow is established according to the proposed method. The measured results from the apparatus agree well with the theoretical calculation results. Both results show that the measuring error is lower than 2.27% when the applicable condition of pressure head is satisfied and the ratio of cross sectional areas of the micro channel and the tube in upper stream is smaller than 3.422%.

Key words: Measurement method, Micro flow, Micropressrue, Non-steady flow, Precision