Research And Implementation Of Echo Energy Integral Based Signal Processing Method For Ultrasonic Gas Flowmeter

Compared with traditional orifice plates,vortex streets,and turbine flowmeters,ultrasonic gas flowmeters have high measurement accuracy and measurement repeatability.Especially in the flow measurement of large-diameter natural gas pipelines,its advantages are more obvious.However,the energy attenuation is severe as the ultrasonic signal propagates through the gas.As the gas flow rate increases,the amplitude of the echo signal becomes smaller,the SNR(Signal-to-Noise Ratio)decreases,and it is easily interfered by noise,resulting in limited measurement accuracy and flow measurement range of the ultrasonic gas flowmeter.From the perspective of the echo energy integral,the change law of the energy of the echo signal is obtained,the signal processing method based on the echo energy integral is proposed,the corresponding parameter selection method is put forward.This method can accurately find the feature points of the echo signal,and then calculate the forward and backward flow propagation time of the ultrasonic signal to complete the measurement of the gas flow rate.The anti-interference ability of the signal processing method under noisy flow and pulsating flow is simulated by simulation experiments.It showed that the method has high fault tolerance and has a certain suppression effect on the noise in the echo signal band.The above signal processing method is realized in real time on a dual core system based on DSP and FPGA,it effectively increases the accuracy of the measurement and widens the range of measurable flow.In order to verify the effectiveness of the signal processing method and development system,the calibration experiments was carried out at the Institute of Metrology of Anhui Province.The experimental results show that the two-channel ultrasonic gas flowmeter based on echo energy integration,its indication error and repeatability meet the requirements of the national standard for the accuracy of the 1-level ultrasonic gas flowmeter.The developed system not only has high real-time performance,but also has a maximum measurable flow rate of 1200 m3/h and a turndown ratio of 1:120,which effectively widens the measurement range of the ultrasonic gas flowmeter.