Underwater Ultrasonic sensor is mainly used for Pool Cleaning Robots, the product utilizes ultrasonic measurement principle, due to the inverse piezoelectric eect of ultrasonic waves, when propagated in the water, encountered obstacles after the reflection of the return wave, was received by the sensor, the built-in circuitry of the received signals to the digital conversion, and through the MCU according to the principle of the TOF calculated the distance from the obstacle. The protection level of the product reaches IP68, which can be immersed underwater for a long time, and the material is corrosion-resistant and not easy to be damaged.