Complex signal processing for Coriolis mass flow metering in two-phase flow

This paper presents new complex signal processing methods, Complex Bandpass Filtering (CBF), Complex Notch Filtering (CNF) and their combination (CBF-CNF), applied to the Coriolis Mass Flowmeter (CMFM). CBF, CNF and CBF-CNF can be utilized to suppress the negative frequency component of each sensor signal in order to produce the corresponding analytic form with reduced tracking delay. Further processing of the analytic form yields the amplitude, frequency, phase and phase difference of the sensor signals. In comparison with previously published methods, the new techniques offer short delay, high noise suppression, high accuracy and low computational cost. A reduced delay is useful in CMFM signal processing especially for maintaining flowtube oscillation in two/multi-phase flow conditions. The central frequency and the frequency range for the CBF, CNF and CBF-CNF methods are selectable so that they can be customized for different flowtube designs.