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Coriolis mass flowmeters (CMFs) have been widely used in industry because of its high precision (up to 0.1% on flow rig). A precondition to ensure the excellent performance of a CMF is that its measuring tube must vibrate with proper amplitude under different operating conditions. It is thus necessary to modify the driving force of its electromagnetic actuator (EMA), which however cannot be measured directly by means of a traditional force sensor. This paper presents an analytical model for calculating the EMA force of a CMF providing a means to predict some parametric effects on its performance. Specifically, the analytical model of a curved-tube CMF has been derived in closed forms for reconstructing the magnetic field from measured boundary conditions, and for calculating the Lorentz force of a permanent-magnet (PM)-based EMA in this paper. This novel coupled measurement-calculation approach, which relaxes the assumption of known magnetic property of the PM, has been validated through a series of experiments and applied to actual CMF offering insightful findings for designing EMA in CMF applications. Two sets of results are presented. The first set investigates the effect of two different loads on the vibration amplitude. The second set reveals the influence of vibration amplitudes on the Lorentz force of the EMA.
Date of Publication: Dec. 2012