Modelling and tracking a vortex flow-meter signal

The piezoelectric sensor in a vortex-shedding flow meter produces a raw signal whose average frequency indicates volumetric flow rate. Imposed on this signal are amplitude and frequency variations, together with noise caused by plant-specific pressure pulsations. The objective of this paper is to provide and verify a simulation model of the overall signal, so that different frequency-tracking methods can be compared. In particular the performance of a zero-crossing algorithm is evaluated. A prefilter is designed to extend the tracking ability to lower flow rates, where the signal:noise ratio is poor. Experimental tests in real time on a flow rig demonstrate the improvement in turn-down by a factor of two. (C) 2002 Elsevier Science Ltd. All rights reserved.