In recent years, with the deepening of ultrasonic technology research, coupled with its advantages of high precision, non-destructive and non-contact, the application of ultrasonic is becoming more and more popular. At present, it has been widely used in machinery manufacturing, electronic metallurgy, navigation, aviation, aerospace, petrochemical industry, transportation and other industrial fields. In addition, it also plays an important role in the fields of materials science, medicine and biological science.
In China, the large-scale research on ultrasound began with 1956. So far, research and application have been carried out in various fields of ultrasound, and a few of them have approached or reached the international level.
Li Maoshan of China Testing Technology Research Institute elaborated the principle of ultrasonic ranging in detail in Principle and Practical Technology of Ultrasonic ranging, gave the concrete block diagram of ultrasonic ranging, and discussed several reasons that affected the accuracy of ultrasonic ranging. In this paper, he did not mention some specific circuits needed for ultrasonic ranging, but only gave the names of circuits generally needed for ranging, without mentioning the matching between various circuits.
1998, manis matek (Qinhuangdao) co., ltd introduced a digital ultrasonic displacement measuring instrument. Li Zhongjie introduced the structure, working principle and function of this digital ultrasonic displacement measuring instrument in the article "Research on Digital Ultrasonic Displacement Measuring Instrument". With the help of single board computer, the program block diagram is given, the hardware circuits of each part of the instrument are explained in detail, and the measurement data of some instruments are listed and analyzed. In this paper, the advantages of ultrasonic range finder in measuring the displacement of hydraulic cylinder compared with other displacement sensors are given, and the program block diagram of single chip microcomputer is given. Wang Runtian of Shanghai Acoustics Laboratory of China Academy of Sciences put forward the principle and method of dual-frequency ultrasonic ranging in his article "Dual-frequency ultrasonic ranging". Because the absorption of ultrasonic waves by air is proportional to the square of ultrasonic waves, the ultrasonic frequency used for ranging cannot be very high, but on the other hand, the lower the frequency, the longer the wavelength, the greater the absolute error of the measurement length, and the widening of the ranging range is actually contradictory to the measurement accuracy. Wang Runtian proposed that to achieve long-distance ranging accuracy, two kinds of ultrasonic waves should be emitted at the same time, with the larger frequency measuring short distance and the smaller frequency measuring long distance, so as to achieve higher ranging accuracy in a wider range.
With the continuous development and wide application of computer technology, automation technology and industrial robots, ranging becomes more and more important. At present, the commonly used ranging methods mainly include radar ranging, infrared ranging, laser ranging and ultrasonic ranging. Compared with other ranging methods, ultrasonic ranging has the following advantages:
(1) Ultrasonic wave is insensitive to color and illumination, and can be used to identify objects with poor transparency and large diffuse reflection (such as glass and polished objects).
(2) Ultrasonic waves are insensitive to external light and electromagnetic fields, and can be used in dark, dust or smoke, strong electromagnetic interference, toxic and other harsh environments.
(3) The ultrasonic sensor has the advantages of simple structure, small volume, low cost, low technical difficulty, simple and reliable information processing, and easy miniaturization and integration. Therefore, ultrasound, as a means of distance measurement and identity recognition, has attracted more and more attention.