Hand-held ultrasonic flow meters enable non-contact measurement of liquid flow. The flow is measured by mounting the sensor on the outer wall of the pipe. It has the characteristics of small size, convenient carrying and accurate measurement. It is widely used in tap water, heating, water conservancy, metallurgy, chemical, machinery, energy and other industries. It can be used for production monitoring, flow verification, flow inspection, water balance adjustment, energy saving monitoring, and is an essential tool for real-time flow detection.