超声波传感器是将超声波信号转换成其他能量信号（通常是电信号）的传感器。超声波是振动频率高于20KHz的机械波。它具有频率高、波长短、绕射现象小，特别是方向性好、能够成为射线而定向传播等特点。超声波对液体、固体的穿透本领很大，尤其是在阳光不透明的固体中。超声波碰到杂质或分界面会产生显著反射形成反射成回波，碰到活动物体能产生多普勒效应。超声波传感器广泛应用在工业、国防、生物医学等方面。(Ultrasonic sensor is a transducer that converts ultrasonic signal to other energy signals (usually electrical signals). Ultrasonic wave is a mechanical wave with a vibration frequency higher than 20KHz. It has the characteristics of high frequency, short wavelength and small diffraction phenomenon, especially good directional, being able to become a ray and directional propagation. Ultrasound has great penetrating power to liquids and solids, especially in opaque sunlight. When ultrasonic meets impurity or interface, it will produce significant reflection, form reflection to echo, and encounter moving object can produce Doppler effect. Ultrasonic sensors are widely used in industry, national defense, biomedicine and so on.)