We generally refer to sonic waves whose sound wave frequency exceeds 20 kHz as ultrasonic waves. Ultrasonic waves are a kind of mechanical waves, that is, a kind of mechanical vibration propagation process in elastic media. It is characterized by high frequency, short wavelength, and small diffraction phenomenon. With good directionality, it can be ray and directed. Ultrasonic waves have small attenuation in liquids and solids, so they have strong penetrating power. Especially in solids that are opaque to light, ultrasonic waves can penetrate several tens of meters in length. When they encounter impurities or interfaces, they will have significant reflections. Ultrasonic measurement Levels take advantage of this feature.
In the ultrasonic detection technology, no matter what kind of ultrasonic instrument, it must send out the electric energy conversion ultrasonic wave, and then receive back and transform it into the electric signal. The device that accomplishes this function is called the ultrasonic transducer, also called probe. As shown in the figure, the ultrasonic transducer is placed above the liquid to be measured, and the ultrasonic wave is emitted downward. The ultrasonic wave passes through the air medium and is reflected back when it meets the water surface, and is received by the transducer and converted into an electric signal. The electronic detection section detects this signal and turns it into a liquid level signal for display and output.
According to the principle of ultrasonic propagation in the medium, if the conditions such as medium pressure, temperature, density, and humidity are constant, the propagation speed of ultrasonic waves in the medium is a constant. Therefore, when measuring the time required for the ultrasonic wave to reach the liquid surface reflection after it is emitted, the distance traveled by the ultrasonic wave can be converted, that is, the liquid level data can be obtained. Water depth H=S-V.t/2