Coriolis Flowmeter Verification via Embedded Modal Analysis

Verification of industrial flowmeters can be a costly endeavor, requiring significant factory downtime, but is often required to ensure measurement accuracy. A new feature, called Smart Meter Verification, now available on Coriolis meters uses embedded experimental modal analysis to confirm flowmeter accuracy. Smart Meter Verification has been successfully employed by numerous customers and has generated significant revenue. This paper outlines the evolution of this product from an offline, lab-based, concept to an embedded product. The embedded modal analysis fits a single degree of freedom model to the primary drive mode, based on frequency response measurements made at select tones near the drive mode. The estimated stiffness from each verification’s modal analysis is compared to the stiffness from a factory baseline to ensure that the meter is still within calibration. Simultaneous multi-tonal excitation of the meter is used to maximize the usable signal generated from a limited excitation power budget, to cope with a time-varying system, and to minimize the complications of nonlinearity. MATLAB-based rapid software prototyping was used to prototype these embedded algorithms on a real-time DSP platform. Excitation of the flowmeter and measurement of response is performed using the transducers already on the device, and the model fit and control logic are performed using the existing embedded electronics. This has allowed the verification technique to be applied without changing the design of the flowmeter hardware.