Study On Coriolis Mass Flowmeter Transmitter Based On DSP System

The Coriolis Mass Flowmeter has been widely used in many industries,for its advantages of direct measuring,better zero stability,better repeatability and higher accuracy and so on.However,the core technologies of Coriolis Mass Flowmeter are still monopolied by foreign companies,especially the transmitter system.Therefore,researching and designing the transmitter system are very important to improve the development status of the domestic flowmeters.This paper is organized as follows:firstly,it introduces the status of development and research of the Coriolis Mass Flowmeter at home and abroad,and also presents its working principle,composition and classification in brief.Then,some novel signal processing schemes are proposed to solve the limitations of signal processing at the measurement of stable single-flow and complex flow respectively.At last,the transmitter based on DSP controller TMS320F28335 is designed and tested,including hardware and software.To settle the problem of large measurement error of stable single-phase fluid,a novel method based on Hilbert Transform is proposed in this paper.The phase-shift feature of Hilbert Transform is used to calculate the phase-difference between the two sensor signals,and the analytical signal of Hilbert Transform is used to solve the estimated frequency.The simulation results show that the accuracy of the phase measurement is up to 0.02%and the accuracy of the frequency tracking is better than 0.07%.While the complex fluid measurement is susceptible to be disturbed and its calculation is complicated,a method combined adaptive notch filter algorithm based on Steiglitz-McBride(referred to as SMM)with calculating phase-difference on Hilbert Transform is introduced in this paper.The method combines the former which simple and fast convergence with the latter which has high calculating accuracy but without any convergence processes,so it can improve the speed and accuracy of frequency tracking.While designing the Coriolis Transmitter based on DSP controller chip of TMS320F28335,a series of measures are put forward to ensure the realization of the proposed algorithm.In the design of hardware,a high-performance multi-channel synchronous acquisition ADC is used to capture two sensor signals accurately,and the cutoff frequency of filter is designed accurately to solve the problem of phase shift.In the design of software,the double precision real type variable,the average value processing and the DMA transfer mode and other measures are adopted to improve the accuracy and speed of data processing.Finally,the experimental calibration and tests for the designed Flowmeter Transmitter are completed.For the stable single-phase fluid,the ratio of measurement range can reach 10:1 and the accuracy is better than 0.1%.Experimental results show that the designed flowmeter transmitter system has better performance and superior algorithm,so it has good prospects.