The working principle of the ultrasonic level meter is that the high frequency ultrasonic pulse emitted by the transducer (probe) is reflected back from the surface of the measured medium, and part of the reflected echo is received by the same transducer and converted into an electric signal. The ultrasonic pulse propagates at the speed of the sound wave, and the time interval from transmitting to receiving the ultrasonic pulse is proportional to the distance from the transducer to the surface of the measured medium. The relationship between this distance value S and the speed of sound C and the transmission time T can be expressed by the formula: S=CxT/2.
According to the above principles, the application of ultrasonic level meters mainly has the following limitations:
First, ultrasonic level meters cannot be used in a vacuum environment. Ultrasound is a kind of mechanical sound wave. It must have medium as a conductive medium, so it cannot be used in a vacuum environment. When the transmission medium changes, the sound speed of the ultrasonic wave will change, which will seriously affect the accuracy of the measurement. Therefore, it cannot be applied to an environment where the propagation medium frequently changes.
Second, ultrasonic level gauges cannot be used in high temperature and high pressure applications. The speed of ultrasonic sound propagation C is greatly affected by the temperature and pressure changes of the propagation medium. Although it has a built-in temperature compensation mechanism, temperature compensation can only be performed within a certain range. Exceeding the temperature compensation range will seriously affect the measurement accuracy. Therefore, the ultrasonic level gauge is sensitive to temperature and pressure and is not suitable for high temperature and high pressure applications.
Third, ultrasonic level gauges are rarely used for the measurement of solid materials. Ultrasound is a kind of mechanical sound energy. In the process of propagation, if it encounters strong absorption of sound energy materials, it will seriously affect the measurement accuracy and even cause the ultrasonic level gauge to fail to measure. Especially for the denser evacuation of solid powder, because of the strong absorption of the material, it will cause sound waves to be absorbed by the material and cannot form reflections. Therefore, the ultrasonic level gauge is generally applied to the measurement of liquids.
Fourth, when the ultrasonic level meter is in use, it is necessary to reserve the margin of the blind area. Since the transmitted ultrasonic pulse has a certain width, the reflected wave and the transmitted wave in a small area near the transducer overlap, and cannot be identified, and the distance cannot be measured. This area is called a measurement blind zone. Due to the presence of blind spots, the use of ultrasonic level timing requires a margin of blindness on the device under test.
The above is related to the "Ultrasonic Level Meter Application Limitations". For more information on level switches, magnetic level gauges and other level measuring instruments, please pay attention to WeChat public number: Jiweimeter. (The article is taken from:, please indicate the source.)
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