Working principle of Ultrasonic Ranging:
The frequency of the sound that people can hear is: 20Hz ~ 20kHz, that is, audible sound wave. The sound beyond this frequency range, that is, the sound below 20Hz is called low-frequency sound wave, and the sound above 20kHz is called ultrasonic wave. Ultrasound is a kind of mechanical wave that can only be felt by a few organisms (bats and dolphins), whose frequency is above 20kHz, wavelength is short, diffraction is small, and directional transmission can be achieved. The higher the frequency, the weaker the diffraction ability, but the stronger the reflection ability. Therefore, ultrasonic sensor can be made by using this property of ultrasonic.
The principle of ultrasonic distance measurement is to use the ultrasonic transmitter to send ultrasonic wave in a certain direction. At the same time, the timing starts. When the ultrasonic wave propagates in the air, it immediately returns when it encounters obstacles on the way, and when the ultrasonic receiver receives the reflected wave, it immediately stops timing. The propagation speed of ultrasound in the air is 340m / s. according to the time t recorded by the timer, the distance (s) between the starting point and the obstacle can be calculated, that is, s = 340t / 2.
The circuit function modules of ultrasonic ranging system include transmitting circuit, receiving circuit, keyboard display circuit, core function module MCU controller and some auxiliary circuits. There are two advantages to adopt the method of separation of receiving and sending: one is that the receiving and sending signals will not be overlapped, and the received signals from the receiving probe are purely reflected signals; the other is that the receiving probe is placed in a proper position, which can avoid all kinds of losses and interference caused by ultrasonic reflection on the surface of the object, and improve the reliability of the system.
In recent years, with the development of microelectronics technology, the emergence of small and cheap microprocessor (single chip microcomputer) has improved the function of ultrasonic ranging sensor. With the microprocessor, not only the accuracy of ranging is greatly improved, but also the application of ultrasonic ranging technology opens up more space.