Method for CMF Signal Processing Based on the Recursive DTFT Algorithm With Negative Frequency Contribution

There is a long convergence stage when using the sliding Goertzel algorithm to measure the phase difference between signals of a Coriolis mass flowmeter (CMF) because the contribution of negative frequency is neglected in the algorithm. A novel method for CMF signal processing is proposed based on the recursive discrete-time Fourier transform (DTFT) algorithm with negative frequency contribution. First, an adaptive lattice notch filter is applied to filter the sensor output signals of the CMF and calculate the frequency. Then, a new method based on the recursive DTFT algorithm with negative frequency contribution is introduced to calculate the real-time phase difference between two enhanced signals. With the frequency and the phase difference obtained, the time interval of the two signals is calculated, and then, the mass flowrate is derived. The method is validated in experiments using CMF signals acquired for different flowrates. Simulation and experimental results show that the convergence stage of both the phase difference and time interval calculations has been largely shortened with higher accuracy of the CMF, as compared with the existing method based on the sliding Goertzel algorithm.