Principle of ultrasonic sensor is the use of ultrasonic characteristics of the sensor developed. Ultrasonic is a vibration frequency higher than the sound wave mechanical waves, vibration generated by the transducer chip in the voltage excitation, it has a high frequency, short wavelength, small bypass phenomenon, in particular, good directionality, can become a ray and directional propagation and other characteristics. Ultrasonic penetration of liquids, solids, especially in the sun opaque solids, it can penetrate the depth of tens of meters. Ultrasound encounters impurities or interfaces will produce significant reflections to form reflections into echoes, and can produce the Doppler effect when it encounters moving objects. Therefore, ultrasonic detection is widely used in industry, national defense, biomedical and other aspects of ultrasound as a means of detection, must produce ultrasound and receive ultrasound. Completion of this function of the device is the ultrasonic sensor, customarily known as ultrasonic transducer, or ultrasonic probe. Ultrasonic level sensor composition ultrasonic sensor is mainly composed of piezoelectric wafer, can transmit ultrasonic waves, but also can receive ultrasonic waves. The low power ultrasonic probe is mostly used as a probe. It has many different structures, which can be divided into straight probe (longitudinal wave), oblique probe (transverse wave), surface wave probe (surface wave), Lamb wave probe (Lamb wave), double probe (a probe to reflect, a probe to receive) and so on. The heart of an ultrasound transducer is a piezoelectric wafer in its plastic jacket or metal jacket. There can be many different materials that make up the wafer. The size of the wafer, such as diameter and thickness, also varies, so the performance of each sensor is different, and we must know its performance in advance before use. Ultrasonic Level SensorThe main performance indicators of ultrasonic sensors. Operating frequency. The operating frequency is the *** vibration frequency of the piezoelectric wafer. When added to its ends of the frequency of the AC voltage and the wafer's *** vibration frequency is equal, the output energy is the largest, the highest sensitivity. Operating temperature. Because the Curie point of piezoelectric materials is generally high, especially when the diagnostic ultrasound probe using low power, so the operating temperature is relatively low, can work for a long time without failure. Medical ultrasound transducers have higher temperatures and require separate refrigeration equipment. Sensitivity. Depends largely on the manufacturing wafer itself. A high electromechanical coupling coefficient results in high sensitivity; conversely, low sensitivity. As in the case of ultrasonic transducers, a composite shaker is flexibly fixed to the base. The composite vibrator is a combination of a resonator and a dual piezoelectric wafer element vibrator consisting of a metal wafer and a piezoelectric ceramic wafer. The resonator is horn shaped in order to efficiently radiate ultrasonic waves generated due to vibration and to efficiently concentrate the ultrasonic waves in the central part of the vibrator. Ultrasonic sensors for outdoor use must be well sealed so as to protect against dew, rain and dust. The piezoelectric ceramic is secured to the inside of the top of the metal cassette. The base is fixed to the open end of the cassette and is covered with resin. For ultrasonic sensors for industrial robots, an accuracy of 1 mm and strong ultrasonic radiation are required.