Research On Digital Vortex Flowmeter With Double MSP430 Single Chip Microcomputers

The vortex flowmeter is widely used in different fields due to its flexibility to various media, without mobile parts, simple structure and long life etc. However, it has poor performance when operating at low flow rate where the Signal-to-Noise ratio is very small or even the signal is submerged by the noise. The traditional analog vortex flowmeter has benefits of steady signal, high accuracy and good real time in the regular flow range, while it also has a disadvantage of weak signal difficult to detect at low flow rate, which leads to unsatisfying lower limit and a smaller range ratio of 10:1.Inasmuch as the advantages and the shortage mentioned above of the analog vortex flowmeter, a digital vortex flowmeter has been developed successfully. The digital vortex flowmeter is made up of a couple of MSP430 single chip microconputers. It identifies the vortex signals from noises by the frequency spectrum analyzing algorithm in MSP430F1611 single chip computer at low flow rate where the analog one is not accurate, or even can't work. Meanwhile it works out by MSP430F149 single chip computer the frequency of the vortex signal that is square waves output from pre-amplifier for the vortex signals in the regular flow range where the Signal-to-Noise ratio isn't too much small, as the analog one is accurate and real time.This paper expatiates with the sequence of the introduction of the vortex flowmeter theory, designment of the hardware and software and analysis of experiment. The main points include:1. The complete circuit and program has been designed. A digital vortex flowmeter with a couple of MSP430 singlechips has been developed successfully. It can choose different method of frequency counting according to variety of the flow and output pulse signal exactly and steadily.2. The digital vortex flowmeter can also output 4～20 mA current. Lots of experiments have been done at DN25 and DN50 pipelines of the water flow experiment facility. It is proved that the digital vortex flowmeter can reduce the disturbance of noise and lower the limit of measurable flow rate. Furthermore, it widens range ratio to 1:35.3～45.5.Lots of experiments on the digital vortex flowmeter have been carried out at DN25 and DN50 pipelines of the water flow experiment facility of Tianjin University. The result shows that the pulse output model digital vortex flowmeter has a satisfying lower limit of measurable flow rate that increases the range ratio effectively, strong antijamming ability and good real time and thus it is of great practicability.