External clamp type or pipe section type ultrasonic flow meter is based on the principle of "velocity difference method". It adopts advanced multi pulse technology, digital signal processing technology and error correction technology, so that the flow meter can adapt to the environment of the industrial field, and the measurement is more convenient, economical and accurate. Products reach the advanced level at home and abroad, can be widely used in petroleum, chemical, metallurgy, electric power, water supply and drainage, and other fields.