Research And Realization Of Excitation And Signal Processing Method About Ultrasonic Gas Flow Meter

Ultrasonic gas flow meter has the advantages of no pressure loss,high measurement precision,wide measuring range and so on.It is widely used in a variety of gas flow measurement,especially in the measurement of large diameter pipeline such as natural gas trade.However,the energy attenuation of the ultrasonic signal is serious and the signal-to-noise ratio of the echo signal is low,which will seriously affect the measurement accuracy and measurement range.The analog signal processing method is entirely adopt in the domestic products,whose measurement accuracy is lower and anti-interfere ability is poor.And the high-end products market is almost monopolized by foreign companies.Therefore,from the view of the excitation method cooperated with the signal processing method,based on the superposition characteristics of waves,a new type of intermittent excitation and signal processing method based on the maximum difference value of adjacent peak are proposed.From the view of the contour of the echo signal,the variation of echo contour is analyzed and the mathematical model for the contour of echo rise is established.One kind of signal processing methods is proposed,which based on the peak fitting of echo signal.Also,from the view of energy envelope of the echo signal,the variation of echo energy is analyzed and the mathematical model for the echo energy envelope is established.One kind of signal processing methods is proposed,which based on the energy point positioning of echo signal.On the hardware systems based on DSP(Digital Signal Processor)and FPGA(Field-Programmable Gate Arrays),the above signal processing methods and excitation method are achieved in time,which can effectively improve the measurement accuracy of the ultrasonic gas flow meter and extended the measurement range.The ultrasonic gas flow meter calibration experiments are conducted in the Anhui Institute of Measurement.The experimental results show that the accuracy of the two-channel ultrasonic gas flow meter,founded on three signal processing methods including based on the maximum difference value of adjacent peak,the peak fitting of echo and the energy point positioning of echo signal,meet the national standard requirements for 1-level precision of ultrasonic gas flow meter.Their measurement accuracy has reached the highest level of similar products at home and abroad.Moreover,compared with the similar products at home and abroad,the maximum measurable flow rate of the developed ultrasonic gas flow meter increased to about 1.53 times,effectively widening the measurement range.