A vortex flowmeter based on multiprocessor technique

Vortex flow meter is widely used in industries because of its many advantages. However, it is subjected to the influence of noise when it works at low flow rate. The useful vortex signal is weak and easily drowned by noises, so it´s measurement accuracy can´t be ensured and the turn-down ratio is limited. In order to solve the problem, a secondary instrument system of vortex flow meter is presented in this paper. This system is based on a digital signal processor (DSP) and mixed signal processor 430 (MSP430). A switched capacitor filter (SCF) was designed in the analog circuit using MSP430 as programmable clock source. Hilbert-Huang transform (HHT) frequency estimation method was used to process the sensor signal. It is indicated that the system can not only retrieve the useful vortex signal exactly but also extend the lower measurement limit of vortex flow meter.