Patent ID: 7684938

Claim:
An ultrasonic flow sensor for measuring a rate of flow of a fluid, the sensor comprising: a spaced-apart pair of ultrasonic transducers, each transducer acoustically coupled to a first side of a respective acoustic window having a respective second side wetted by the fluid when the fluid is present; a measurement signal generating circuit operable, when connected to the ultrasonic transducers, to generate a measurement acoustic signal therefrom, the measurement acoustic signal characterized by a measurement signal frequency of at least five hundred kilohertz; a signal processing circuit operable, when connected to the ultrasonic transducers, to receive an electrical measurement signal therefrom at the measurement signal frequency, the signal processing circuit further operable to output a signal representative of the rate of flow of the fluid; and a cleaning signal generating circuit operable, when connected to at least one of the ultrasonic transducers, to generate an acoustic cleaning signal therefrom, the acoustic cleaning signal characterized by a cleaning signal frequency of no more than one hundred kilohertz.