1. College of Electrical and Information Engineering, Hunan University, Changsha, Hunan 410082, China
2. Polytechnic College of Hunan Normal University, Changsha, Hunan 410081, China
Abstract：In order to improve the real-time performance of the liquid-level detection for capillary viscometer and diminish the impact of concave liquid-level and sampling interval on the accuracy of the detection, a liquid-level detection method based on Lagrange parabolic interpolation is proposed. Fiber optic sensors are used as liquid-level detection components. Firstly, the first order difference of the sampling data is figured out. Then Lagrange parabolic interpolation is operated on the sampling data’s first order difference of the sampling time with the least first order difference and its adjacent sampling time. Finally, the timing point is worked out with the time derivative of the interpolation polynomial and the automatic liquid-level detection at the two timing positions is accomplished. Compared with the existing method based on least squares linear fitting, the proposed method has better real-time performance for the less calculation and is less impacted by the sampling interval. Experiments show that the repetitiveness of kinematic viscosity measured with the method is less than 0.1%.
2018, Vol. 39 
