The DSP Algorithm Research And System Development Of Coriolis Mass Flowmeter

The Coriolis Mass Flowmeter (CMF) is widely used in industry due to its following advantages: high measurement accuracy, being able to measure fluid mass directly and measure various parameters of fluid. Usually CMF is composed of primary instrument and secondary instrument. Primary instrument includes vibrating tube, exciter and sensor. While secondary instrument is to deal with signals from the sensors and measure the mass flow by calculating the phase difference between two channels of signal. The early CMF signal processing is based on analog circuits. As analog signal processing system is riddled with some defects, this paper adopts digital signal processing methods to deal with the signals of CMF.According to the real environment, a reasonable digital signal model is introduced in this paper. Then we research the digital signal processing algorithm of CMF mainly in three aspects: filters, frequency measurement and phase difference measurement. In addition, the research on the CMF prototype is briefly presented, and several modules of software design and code writing are expatiated in this article. The main work of this dissertation shows as follows: 1,The algorithm filtering harmonic in two channel signals is researched with ellipse filter. It does not need another convergence course when the previous signal data has converged to the real signal, so the amount of calculation is smaller and the effect of filter is excellent.2,Referring to the papers in and abroad on adaptive filters, a new adaptive filter algorithm is proposed. The calculation in new algorithm is simpler and the performance is better.3,Phase difference calculation based on recursive DTFT with negative frequency contribution is improved by grouping the datas. The precision is the same as without grouping but grouping algorithm can calculate in parallel and reduce the calculation time.4,Based on the study of conventional sliding Goertzel algorithm, this paper has derived new formulas on the sliding Goertzel algorithm with the changed calculation structure. As a result, the new algorithm can be used in the model not only with fixed sample rate but also with variational sample rate; the calculation time is reduced considerably to achieve the need of real time.5,This paper also designs and debugs several modules of software system for the CMF prototype.