Design and Fabrication of a Four-path Ultrasonic Flowmeter using the Time-difference Method

A four-path ultrasonic flow meter was designed and fabricated by using of ultrasonic transmitter/receivers on an 8-inch pipe. By passing fluid through the flowmeter at a controlled rate, the velocity was measured in different layers using the time-difference method. Fluid flow rate was estimated by Gauss-Legendre numerical integration method and applying of the engineering approximation. By comparison of the results with the actual measurement done by a calibrated reference flow meter, the accuracy of the system was tested at various flow rates. It also was compared with the measurement of an equivalent one-path ultrasonic flowmeter, and the measurement errors were calculated. The test result represented that, the average error of measurement is less than 3% at the speeds of 0.5 m/s and more. The average error was more than 15% at the speeds below 0.3 m/s. The measurement error of the one-path flowmeter was 20% more than that of four path one.