What is an ultrasonic sensor and part of it
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- Time of issue:2020-07-10 13:13
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What is an ultrasonic sensor and part of it
Ultrasonic sensor is a sensor developed by utilizing the characteristics of ultrasonic waves. Ultrasonic wave is a kind of mechanical wave whose vibration frequency is higher than the sound wave, which is generated by the vibration of the energy exchange chip under the excitation of voltage. It has the characteristics of high frequency, short wavelength, small diffraction phenomenon, especially good directivity, and can become ray and directional propagation, etc. Ultrasonic wave to liquid, solid penetration ability is very big, especially in the sunlight opaque solid, it can penetrate tens of meters of depth. Ultrasonic contact with impurities or boundary surface will produce significant reflection to form reflection into echo, touching the moving object can produce Doppler effect. Therefore, ultrasonic testing is widely used in industry, national defense, biomedicine and other aspects to ultrasonic as a means of testing, must produce ultrasonic and receive ultrasonic. The device that performs this function is an ultrasonic transducer, commonly known as an ultrasonic transducer, or ultrasonic probe.
Ultrasonic sensors are mainly composed of piezoelectric wafers, which can transmit and receive ultrasonic waves. Low power ultrasonic probe is used for detection. It has many different structures, can be divided into straight probe (longitudinal wave), oblique probe (transverse wave), surface wave probe (surface wave), lamb wave probe (lamb wave), double probe (one probe reflection, one probe receiving) and so on. The core of the ultrasonic sensor is a piezoelectric chip in its plastic or metal coat. A chip can be made of many kinds of materials. The size of the chip, such as diameter and thickness, also varies, so the performance of each sensor is different, and we must know its performance in advance before using it. The main performance indicators of ultrasonic sensors include :(1) working frequency. The operating frequency is the resonant frequency of the piezoelectric chip. The energy output is maximum and the sensitivity is highest when the frequency of the AC voltage applied to it is equal to the resonance frequency of the chip. (2) Working temperature. Because the Curie point of piezoelectric material is generally high, especially when the ultrasonic probe used for diagnosis USES less power, so the working temperature is relatively low, it can work for a long time without failure. Ultrasonic sensors used in medical applications are high in temperature and require a separate refrigeration unit. (3) Sensitivity. Much depends on making the chip itself. High electromechanical coupling coefficient and high sensitivity; On the contrary, the sensitivity is low.
In the case of ultrasonic sensors, a composite vibrator is flexibly mounted on the base. The composite vibrator is a combination of a resonator and a dual piezoelectric wafer element vibrator consisting of a metal plate and a piezoelectric ceramic plate. The purpose of the resonator is to effectively radiate the ultrasonic waves produced by the vibration and to effectively concentrate the ultrasonic waves at the center of the vibrator.
Ultrasonic sensors for outdoor use must be well sealed to prevent the intrusion of dew, rain and dust. The piezoelectric ceramics are fixed inside the top of the metal box. The base is fixed to the open end of the box body and is covered with resin. For ultrasonic sensors used in industrial robots, the accuracy is required to reach 1mm and have strong ultrasonic radiation.
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