Software Development Of Improved Digital Vortex Flowmeter With Low-power And Two-wire

Digital signal processing technique is applied to the signal processing of vortex flowmeter for improving the measurement accuracy and extending the turn-down radio of vortex flowmeter effectively. The digital signal processing algorithms, however, are implemented by DSPs generally. It cannot meet the requirement of the low-power and two-wire meter due to the high power consumption of DSPs. The performance indexes of the existed vortex flowmeter with low-power and two-wire are not good, e.g. the measurement accuracy is low and turn-down ratio is small, because these meters adopted the conventional signal processing method.In order to solve the aforementioned problems, our group developed a novel two-wire digital vortex flowmeter with a super low-power micro-controller, combining the digital spectrum analysis with the analog band-pass filters. This paper makes great improvement in the system software of the two-wire digital vortex flowmeter. The flags are set by the timer and checked by program to perform the call of the functional modules. The FFT program is developed with the assemble language, and the fixed-point calculation is employed to reduce the computational load and memory space of the algorithm. Before the data are shifted their values are checked first, which can avoid bit growth occurring and ensure the computation accuracy. The multi-period equal- precision measurement method is used to calculate the frequency of the vortex signal, and the measured signal is filled by the standard clock pulse signal to ensure the measurement accuracy. When the frequency bands of adjacent filters overlay, the band-pass filter is selected according to the junction of the frequency band. Averaging and accelerating methods are adopted in flow calculation to ensure the repeatability and reduce the response time. This system has passed the flow tests, and runs normally in the industrial field.