Supersonic flowmeter for open canal

The utility model relates to a supersonic flowmeter for an open canal which comprises a probe head, a signal processing circuit, a measuring and calculating section and an output section, wherein, the probe head is provided with a transmitting circuit, a receiving circuit and a supersonic transducer. The receiving circuit is connected with a signal preamplifying circuit, and a correcting stick is fixedly arranged under the probe head. The signal processing circuit comprises a gating switch, a connecting time increasing part and an automatic increasing part, and is connected with a waveform collecting part. The utility model can be used matching with various measuring weir slots which can fix the water level flow quantity relationship, can overcome the influence from temperature and components, and is suitable for severe environment, with the advantages of high precision, stable performance, convenient and simple operation, strong anti-interference ability.