Ultrasonic Flowmeter for Leakage Detection in Water Mains

This contribution deals with the measurement of very low flow velocities for the use in household water mains to detect small leaks. For this purpose, the ultrasonic time-of-flight principle is exploited. This method is based on different propagation velocities and thus propagation times of the ultrasonic waves with and against the flow direction. This inherently requires the measurement of very small differences between the propagation times in opposing directions. A method to reduce the requirement of resolution of the time measurement or to increase the accuracy of the measurement of the flow velocity for a given resolution is the so-called sing-around technique. In this method, the length of the propagation path is virtually lengthened by sending a new ultrasonic pulse in the same direction immediately after receiving one at the end of the propagation path. This is done N times for both propagation directions and the flow velocity is calculated from the difference of the aggregate propagation times. We present the mechanical setup as well as the necessary electronics for the implementation of the sing-around technique for the measurement of very low flow velocities.