An algorithm is designed for a digital signal processor to perform computations of fast Fourier transform and auto-correlation to determine real-time vortex shedding frequency of a 6″ vortex flowmeter. In the algorithm, a digital band-pass filter which is able to tune its center frequency according to the input signal is arranged at the first step to remove noise components from a vortex shedding signal. After filtering, the vortex shedding signal is utilized to compute vortex shedding frequency, which is done by the technique of auto-correlation as the vortex shedding frequency estimated is less than 200 Hz or by the technique of fast Fourier transform as the frequency estimated is larger than 200 Hz. The test result shows that the maximum error of vortex shedding frequency computed is less than 0.3 % when the vortex flowmeter measures at moderate to higher flow rates. For the case in lowest flow rate, the signal-to-noise ratio for the vortex shedding signal is about 1/12. Even so, the vortex shedding frequency determined is about 1.1% deviated from the true value. Furthermore, the vortex shedding frequency determined by the algorithm has a time lag of 0.512 second from the true vortex shedding frequency as the flow rate is slewing.
|Number of pages||8|
|Journal||Journal of the Chinese Society of Mechanical Engineers, Transactions of the Chinese Institute of Engineers, Series C/Chung-Kuo Chi Hsueh Kung Ch'eng Hsuebo Pao|
|Publication status||Published - 2006 Jun 1|
All Science Journal Classification (ASJC) codes
- Mechanical Engineering